diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b9af8cb..3b026dc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,6 @@ on:
   pull_request:
 
 env:
-  DEVELOPER_NODE: 1
   RETAILCRM_URL: https://test.retailcrm.pro
   RETAILCRM_KEY: key
 
@@ -41,7 +40,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.11', '1.12', '1.13', '1.14', '1.15', '1.16', '1.17']
+        go-version: ['1.13', '1.14', '1.15', '1.16', '1.17']
         include:
           - go-version: '1.17'
             coverage: 1
diff --git a/.gitignore b/.gitignore
index 2650cf3..e1ba55c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@
 
 # Folders
 _obj
+vendor
 
 # Architecture specific extensions/prefixes
 *.[568vq]
diff --git a/.golangci.yml b/.golangci.yml
index 887c5ee..c9b3570 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -146,9 +146,9 @@ linters-settings:
   gocyclo:
     min-complexity: 25
   goimports:
-    local-prefixes: github.com/retailcrm/api-client-go
+    local-prefixes: github.com/retailcrm/api-client-go/v2
   lll:
-    line-length: 120
+    line-length: 160
   maligned:
     suggest-new: true
   misspell:
@@ -180,6 +180,9 @@ issues:
         - gocognit
         - gocyclo
         - godot
+        - gocritic
+        - gosec
+        - staticcheck
   exclude-use-default: true
   exclude-case-sensitive: false
   max-issues-per-linter: 0
diff --git a/README.md b/README.md
index e73f535..9ebb481 100644
--- a/README.md
+++ b/README.md
@@ -10,51 +10,51 @@
 
 This is golang RetailCRM API client.
 
-## Install
+## Installation
 
 ```bash
-go get -x github.com/retailcrm/api-client-go
+go get -u github.com/retailcrm/api-client-go/v2
 ```
 
 ## Usage
 
-```golang
+Example:
+
+```go
 package main
 
 import (
-	"fmt"
-	"net/http"
+	"log"
 
-	"github.com/retailcrm/api-client-go/v5"
+	"github.com/retailcrm/api-client-go/v2"
 )
 
 func main() {
-	var client = v5.New("https://demo.retailcrm.pro", "09jIJ09j0JKhgyfvyuUIKhiugF")
+	var client = retailcrm.New("https://demo.retailcrm.pro", "09jIJ09j0JKhgyfvyuUIKhiugF")
 
-	data, status, err := client.Orders(v5.OrdersRequest{
-		Filter: v5.OrdersFilter{},
+	data, status, err := client.Orders(retailcrm.OrdersRequest{
+		Filter: retailcrm.OrdersFilter{},
 		Limit: 20,
 		Page: 1,
-	},)
+	})
 	if err != nil {
-		fmt.Printf("%v", err.Error())
-	}
+		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+			log.Fatalf("http status: %d, %s", status, apiErr.String())
+        }
 
-	if status >= http.StatusBadRequest {
-		fmt.Printf("%v", err.ApiError())
+		log.Fatalf("http status: %d, error: %s", status, err)
 	}
 
 	for _, value := range data.Orders {
-		fmt.Printf("%v\n", value.Email)
+		log.Printf("%v\n", value.Email)
 	}
 
-	fmt.Println(data.Orders[1].FirstName)
+	log.Println(data.Orders[1].FirstName)
 
-	idata, status, err := c.InventoriesUpload(
-		[]InventoryUpload{
+	inventories, status, err := client.InventoriesUpload([]retailcrm.InventoryUpload{
 			{
 				XMLID: "pTKIKAeghYzX21HTdzFCe1",
-				Stores: []InventoryUploadStore{
+				Stores: []retailcrm.InventoryUploadStore{
 					{
 						Code: "test-store-v5",
 						Available: 10,
@@ -74,7 +74,7 @@ func main() {
 			},
 			{
 				XMLID: "JQIvcrCtiSpOV3AAfMiQB3",
-				Stores: []InventoryUploadStore{
+				Stores: []retailcrm.InventoryUploadStore{
 					{
 						Code: "test-store-v5",
 						Available: 45,
@@ -95,13 +95,70 @@ func main() {
 		},
 	)
 	if err != nil {
-		fmt.Printf("%v", err.Error())
+		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+			log.Fatalf("http status: %d, %s", status, apiErr.String())
+		}
+
+		log.Fatalf("http status: %d, error: %s", status, err)
 	}
 
-	if status >= http.StatusBadRequest {
-		fmt.Printf("%v", err.ApiError())
-	}
-
-	fmt.Println(idata.processedOffersCount)
+	log.Println(inventories.ProcessedOffersCount)
 }
 ```
+
+You can use different error types and `retailcrm.AsAPIError` to process client errors. Example:
+
+```go
+package retailcrm
+
+import (
+	"errors"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/retailcrm/api-client-go/v2"
+)
+
+func main() {
+	var client = retailcrm.New("https://demo.retailcrm.pro", "09jIJ09j0JKhgyfvyuUIKhiugF")
+
+	resp, status, err := client.APICredentials()
+	if err != nil {
+		apiErr, ok := retailcrm.AsAPIError(err)
+		if !ok {
+			log.Fatalf("http status: %d, error: %s", status, err)
+		}
+
+		switch {
+		case errors.Is(apiErr, retailcrm.ErrMissingCredentials):
+			log.Fatalln("No API key provided.")
+		case errors.Is(apiErr, retailcrm.ErrInvalidCredentials):
+			log.Fatalln("Invalid API key.")
+		case errors.Is(apiErr, retailcrm.ErrAccessDenied):
+			log.Fatalln("Access denied. Please check that the provided key has access to the credentials info.")
+		case errors.Is(apiErr, retailcrm.ErrAccountDoesNotExist):
+			log.Fatalln("There is no RetailCRM at the provided URL.")
+		case errors.Is(apiErr, retailcrm.ErrMissingParameter):
+			// retailcrm.APIError in this case will always contain "Name" key in the errors list with the parameter name.
+			log.Fatalln("This parameter should be present:", apiErr.Errors()["Name"])
+		case errors.Is(apiErr, retailcrm.ErrValidation):
+			log.Println("Validation errors from the API:")
+
+			for name, value := range apiErr.Errors() {
+				log.Printf(" - %s: %s\n", name, value)
+			}
+
+			os.Exit(1)
+		case errors.Is(apiErr, retailcrm.ErrGeneric):
+			log.Fatalf("failure from the API. %s", apiErr.String())
+		}
+	}
+
+	log.Println("Available scopes:", strings.Join(resp.Scopes, ", "))
+}
+```
+
+## Upgrading
+
+Please check the [UPGRADING.md](UPGRADING.md) to learn how to upgrade to the new version.
diff --git a/UPGRADING.md b/UPGRADING.md
new file mode 100644
index 0000000..ba68226
--- /dev/null
+++ b/UPGRADING.md
@@ -0,0 +1,70 @@
+# Upgrading to the v2
+
+### Install the new version
+
+```bash
+go get -u github.com/retailcrm/api-client-go/v2
+```
+
+### Update all imports
+
+Before:
+```go
+package main
+
+import v5 "github.com/retailcrm/api-client-go/v5"
+```
+
+After:  
+```go
+package main
+
+import "github.com/retailcrm/api-client-go/v2"
+```
+
+You can use package alias `v5` to skip the second step.
+
+### Replace package name for all imported symbols
+
+Before:
+
+```go
+package main
+
+import v5 "github.com/retailcrm/api-client-go/v5"
+
+func main() {
+    client := v5.New("https://test.retailcrm.pro", "key")
+	data, status, err := client.Orders(v5.OrdersRequest{
+		Filter: v5.OrdersFilter{
+			City: "Moscow",
+		},
+		Page: 1,
+	})
+	...
+}
+```
+
+After:
+
+```go
+package main
+
+import "github.com/retailcrm/api-client-go/v2"
+
+func main() {
+    client := retailcrm.New("https://test.retailcrm.pro", "key")
+	data, status, err := client.Orders(retailcrm.OrdersRequest{
+		Filter: retailcrm.OrdersFilter{
+			City: "Moscow",
+		},
+		Page: 1,
+	})
+	...
+}
+```
+
+### Upgrade client usages
+
+This major release contains some breaking changes regarding field names and fully redesigned error handling. Use the second example from 
+the readme to learn how to process errors correctly.
diff --git a/v5/client.go b/client.go
similarity index 65%
rename from v5/client.go
rename to client.go
index 122e200..89c56a8 100644
--- a/v5/client.go
+++ b/client.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 import (
 	"bytes"
@@ -26,16 +26,29 @@ func New(url string, key string) *Client {
 	}
 }
 
+// WithLogger sets the provided logger instance into the Client.
+func (c *Client) WithLogger(logger BasicLogger) *Client {
+	c.logger = logger
+	return c
+}
+
+// writeLog writes to the log.
+func (c *Client) writeLog(format string, v ...interface{}) {
+	if c.logger != nil {
+		c.logger.Printf(format, v...)
+		return
+	}
+
+	log.Printf(format, v...)
+}
+
 // GetRequest implements GET Request.
 func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte, int, error) {
 	var res []byte
 	var prefix = "/api/v5"
-	apiError := &APIError{}
 
 	if len(versioned) > 0 {
-		s := versioned[0]
-
-		if s == false {
+		if !versioned[0] {
 			prefix = "/api"
 		}
 	}
@@ -48,7 +61,7 @@ func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte
 	req.Header.Set("X-API-KEY", c.Key)
 
 	if c.Debug {
-		log.Printf("API Request: %s %s", fmt.Sprintf("%s%s%s", c.URL, prefix, urlWithParameters), c.Key)
+		c.writeLog("API Request: %s %s", fmt.Sprintf("%s%s%s", c.URL, prefix, urlWithParameters), c.Key)
 	}
 
 	resp, err := c.httpClient.Do(req)
@@ -57,8 +70,8 @@ func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte
 	}
 
 	if resp.StatusCode >= http.StatusInternalServerError {
-		apiError.ErrorMsg = fmt.Sprintf("HTTP request error. Status code: %d.\n", resp.StatusCode)
-		return res, resp.StatusCode, apiError
+		return res, resp.StatusCode, CreateGenericAPIError(
+			fmt.Sprintf("HTTP request error. Status code: %d.", resp.StatusCode))
 	}
 
 	res, err = buildRawResponse(resp)
@@ -67,11 +80,11 @@ func (c *Client) GetRequest(urlWithParameters string, versioned ...bool) ([]byte
 	}
 
 	if resp.StatusCode >= http.StatusBadRequest && resp.StatusCode < http.StatusInternalServerError {
-		return res, resp.StatusCode, NewAPIError(res)
+		return res, resp.StatusCode, CreateAPIError(res)
 	}
 
 	if c.Debug {
-		log.Printf("API Response: %s", res)
+		c.writeLog("API Response: %s", res)
 	}
 
 	return res, resp.StatusCode, nil
@@ -89,7 +102,6 @@ func (c *Client) PostRequest(
 	)
 
 	prefix := "/api/v5"
-	apiError := &APIError{}
 
 	if len(contType) > 0 {
 		contentType = contType[0]
@@ -111,7 +123,7 @@ func (c *Client) PostRequest(
 	req.Header.Set("X-API-KEY", c.Key)
 
 	if c.Debug {
-		log.Printf("API Request: %s %s", uri, c.Key)
+		c.writeLog("API Request: %s %s", uri, c.Key)
 	}
 
 	resp, err := c.httpClient.Do(req)
@@ -120,8 +132,8 @@ func (c *Client) PostRequest(
 	}
 
 	if resp.StatusCode >= http.StatusInternalServerError {
-		apiError.ErrorMsg = fmt.Sprintf("HTTP request error. Status code: %d.\n", resp.StatusCode)
-		return res, resp.StatusCode, apiError
+		return res, resp.StatusCode, CreateGenericAPIError(
+			fmt.Sprintf("HTTP request error. Status code: %d.", resp.StatusCode))
 	}
 
 	res, err = buildRawResponse(resp)
@@ -130,11 +142,11 @@ func (c *Client) PostRequest(
 	}
 
 	if resp.StatusCode >= http.StatusBadRequest && resp.StatusCode < http.StatusInternalServerError {
-		return res, resp.StatusCode, NewAPIError(res)
+		return res, resp.StatusCode, CreateAPIError(res)
 	}
 
 	if c.Debug {
-		log.Printf("API Response: %s", res)
+		c.writeLog("API Response: %s", res)
 	}
 
 	return res, resp.StatusCode, nil
@@ -197,20 +209,20 @@ func fillSite(p *url.Values, site []string) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.APIVersions()
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.versions {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) APIVersions() (VersionResponse, int, error) {
 	var resp VersionResponse
@@ -220,7 +232,10 @@ func (c *Client) APIVersions() (VersionResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -231,20 +246,20 @@ func (c *Client) APIVersions() (VersionResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.APICredentials()
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
+//
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
-// 	}
-//
-// 	for _, value := range data.credentials {
-// 		fmt.Printf("%v\n", value)
+// 	for _, value := range data.Scopes {
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) APICredentials() (CredentialResponse, int, error) {
 	var resp CredentialResponse
@@ -254,7 +269,10 @@ func (c *Client) APICredentials() (CredentialResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -265,9 +283,9 @@ func (c *Client) APICredentials() (CredentialResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Customers(v5.CustomersRequest{
+// 	data, status, err := client.Customers(retailcrm.CustomersRequest{
 //		Filter: CustomersFilter{
 //			City: "Moscow",
 //		},
@@ -275,15 +293,15 @@ func (c *Client) APICredentials() (CredentialResponse, int, error) {
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.Customers {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Customers(parameters CustomersRequest) (CustomersResponse, int, error) {
 	var resp CustomersResponse
@@ -295,7 +313,10 @@ func (c *Client) Customers(parameters CustomersRequest) (CustomersResponse, int,
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -306,16 +327,16 @@ func (c *Client) Customers(parameters CustomersRequest) (CustomersResponse, int,
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomersCombine([]v5.Customer{{ID: 1}, {ID: 2}}, Customer{ID: 3})
+// 	data, status, err := client.CustomersCombine([]retailcrm.Customer{{ID: 1}, {ID: 2}}, Customer{ID: 3})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -324,8 +345,8 @@ func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer)
 	combineJSONOut, _ := json.Marshal(&resultCustomer)
 
 	p := url.Values{
-		"customers":      {string(combineJSONIn[:])},
-		"resultCustomer": {string(combineJSONOut[:])},
+		"customers":      {string(combineJSONIn)},
+		"resultCustomer": {string(combineJSONOut)},
 	}
 
 	data, status, err := c.PostRequest("/customers/combine", p)
@@ -333,7 +354,10 @@ func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer)
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -344,30 +368,30 @@ func (c *Client) CustomersCombine(customers []Customer, resultCustomer Customer)
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomersCombine(v5.Customer{
+// 	data, status, err := client.CustomersCombine(retailcrm.Customer{
 //		FirstName:  "Ivan",
 //		LastName:   "Ivanov",
 //		Patronymic: "Ivanovich",
 //		ExternalID: 1,
 //		Email:      "ivanov@example.com",
-//		Address: &v5.Address{
+//		Address: &retailcrm.Address{
 //			City:     "Moscow",
 //			Street:   "Kutuzovsky",
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-//		fmt.Printf("%v", err.Id)
+//		fmt.Printf("%v", data.ID)
 //	}
 func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChangeResponse, int, error) {
 	var resp CustomerChangeResponse
@@ -375,7 +399,7 @@ func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChan
 	customerJSON, _ := json.Marshal(&customer)
 
 	p := url.Values{
-		"customer": {string(customerJSON[:])},
+		"customer": {string(customerJSON)},
 	}
 
 	fillSite(&p, site)
@@ -385,7 +409,10 @@ func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChan
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -396,19 +423,19 @@ func (c *Client) CustomerCreate(customer Customer, site ...string) (CustomerChan
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomersFixExternalIds([]v5.IdentifiersPair{{
+// 	data, status, err := client.CustomersFixExternalIds([]retailcrm.IdentifiersPair{{
 //		ID:         1,
 //		ExternalID: 12,
 //	}})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -416,7 +443,7 @@ func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (Successfu
 	customersJSON, _ := json.Marshal(&customers)
 
 	p := url.Values{
-		"customers": {string(customersJSON[:])},
+		"customers": {string(customersJSON)},
 	}
 
 	data, status, err := c.PostRequest("/customers/fix-external-ids", p)
@@ -424,7 +451,10 @@ func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (Successfu
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -435,24 +465,24 @@ func (c *Client) CustomersFixExternalIds(customers []IdentifiersPair) (Successfu
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomersHistory(v5.CustomersHistoryRequest{
-//		Filter: v5.CustomersHistoryFilter{
+// 	data, status, err := client.CustomersHistory(retailcrm.CustomersHistoryRequest{
+//		Filter: retailcrm.CustomersHistoryFilter{
 //			SinceID: 20,
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.History {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (CustomersHistoryResponse, int, error) {
 	var resp CustomersHistoryResponse
@@ -464,7 +494,10 @@ func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (Customers
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -475,25 +508,25 @@ func (c *Client) CustomersHistory(parameters CustomersHistoryRequest) (Customers
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomerNotes(v5.NotesRequest{
-//		Filter: v5.NotesFilter{
+// 	data, status, err := client.CustomerNotes(retailcrm.NotesRequest{
+//		Filter: retailcrm.NotesFilter{
 //			CustomerIds: []int{1,2,3}
 // 		},
 //		Page: 1,
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.Notes {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, error) {
 	var resp NotesResponse
@@ -505,7 +538,10 @@ func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, err
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -516,26 +552,26 @@ func (c *Client) CustomerNotes(parameters NotesRequest) (NotesResponse, int, err
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomerNoteCreate(v5.Note{
+// 	data, status, err := client.CustomerNoteCreate(retailcrm.Note{
 //		Text:      "some text",
 //		ManagerID: 12,
-//		Customer: &v5.Customer{
+//		Customer: &retailcrm.Customer{
 //			ID: 1,
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -543,7 +579,7 @@ func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse,
 	noteJSON, _ := json.Marshal(&note)
 
 	p := url.Values{
-		"note": {string(noteJSON[:])},
+		"note": {string(noteJSON)},
 	}
 
 	fillSite(&p, site)
@@ -553,7 +589,10 @@ func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse,
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -564,15 +603,15 @@ func (c *Client) CustomerNoteCreate(note Note, site ...string) (CreateResponse,
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.CustomerNoteDelete(12)
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -586,7 +625,10 @@ func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -597,9 +639,9 @@ func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CustomersUpload([]v5.Customer{
+// 	data, status, err := client.CustomersUpload([]retailcrm.Customer{
 //		{
 //			FirstName:  "Ivan",
 //			LastName:   "Ivanov",
@@ -617,15 +659,15 @@ func (c *Client) CustomerNoteDelete(id int) (SuccessfulResponse, int, error) {
 //	}}
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.UploadedCustomers)
+// 		log.Printf("%v\n", data.UploadedCustomers)
 // 	}
 func (c *Client) CustomersUpload(customers []Customer, site ...string) (CustomersUploadResponse, int, error) {
 	var resp CustomersUploadResponse
@@ -633,7 +675,7 @@ func (c *Client) CustomersUpload(customers []Customer, site ...string) (Customer
 	uploadJSON, _ := json.Marshal(&customers)
 
 	p := url.Values{
-		"customers": {string(uploadJSON[:])},
+		"customers": {string(uploadJSON)},
 	}
 
 	fillSite(&p, site)
@@ -643,7 +685,10 @@ func (c *Client) CustomersUpload(customers []Customer, site ...string) (Customer
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -654,20 +699,20 @@ func (c *Client) CustomersUpload(customers []Customer, site ...string) (Customer
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Customer(12, v5.ByExternalID, "")
+// 	data, status, err := client.Customer(12, retailcrm.ByExternalID, "")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Customer)
+// 		log.Printf("%v\n", data.Customer)
 // 	}
 func (c *Client) Customer(id, by, site string) (CustomerResponse, int, error) {
 	var resp CustomerResponse
@@ -681,7 +726,10 @@ func (c *Client) Customer(id, by, site string) (CustomerResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -692,29 +740,29 @@ func (c *Client) Customer(id, by, site string) (CustomerResponse, int, error) {
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CustomerEdit(
-//		v5.Customer{
+//		retailcrm.Customer{
 //			FirstName:  "Ivan",
 //			LastName:   "Ivanov",
 //			Patronymic: "Ivanovich",
 //			ID: 		1,
 //			Email:      "ivanov@example.com",
 //		},
-//		v5.ByID,
+//		retailcrm.ByID,
 //	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Customer)
+// 		log.Printf("%v\n", data.Customer)
 // 	}
 func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (CustomerChangeResponse, int, error) {
 	var resp CustomerChangeResponse
@@ -728,8 +776,8 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 	customerJSON, _ := json.Marshal(&customer)
 
 	p := url.Values{
-		"by":       {string(context)},
-		"customer": {string(customerJSON[:])},
+		"by":       {context},
+		"customer": {string(customerJSON)},
 	}
 
 	fillSite(&p, site)
@@ -739,7 +787,10 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -750,9 +801,9 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomers(v5.CorporateCustomersRequest{
+// 	data, status, err := client.CorporateCustomers(retailcrm.CorporateCustomersRequest{
 //		Filter: CorporateCustomersFilter{
 //			City: "Moscow",
 //		},
@@ -760,15 +811,15 @@ func (c *Client) CustomerEdit(customer Customer, by string, site ...string) (Cus
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.CustomersCorporate {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) CorporateCustomers(parameters CorporateCustomersRequest) (CorporateCustomersResponse, int, error) {
 	var resp CorporateCustomersResponse
@@ -780,7 +831,10 @@ func (c *Client) CorporateCustomers(parameters CorporateCustomersRequest) (Corpo
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -791,22 +845,22 @@ func (c *Client) CorporateCustomers(parameters CorporateCustomersRequest) (Corpo
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomerCreate(v5.CorporateCustomer{
+// 	data, status, err := client.CorporateCustomerCreate(retailcrm.CorporateCustomer{
 //		Nickname:  "Company",
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-//		fmt.Printf("%v", err.Id)
+//		fmt.Printf("%v", data.ID)
 //	}
 func (c *Client) CorporateCustomerCreate(customer CorporateCustomer, site ...string) (
 	CorporateCustomerChangeResponse, int, error,
@@ -816,7 +870,7 @@ func (c *Client) CorporateCustomerCreate(customer CorporateCustomer, site ...str
 	customerJSON, _ := json.Marshal(&customer)
 
 	p := url.Values{
-		"customerCorporate": {string(customerJSON[:])},
+		"customerCorporate": {string(customerJSON)},
 	}
 
 	fillSite(&p, site)
@@ -826,30 +880,33 @@ func (c *Client) CorporateCustomerCreate(customer CorporateCustomer, site ...str
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
 
 // CorporateCustomersFixExternalIds will fix corporate customers external ID's
 //
-// For more information see http://help.retailcrm.pro/Developers/ApiVersion5#post--api-v5-customers-corporate-fix-external-ids
+// For more information see  http://help.retailcrm.pro/Developers/ApiVersion5#post--api-v5-customers-corporate-fix-external-ids
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomersFixExternalIds([]v5.IdentifiersPair{{
+// 	data, status, err := client.CorporateCustomersFixExternalIds([]retailcrm.IdentifiersPair{{
 //		ID:         1,
 //		ExternalID: 12,
 //	}})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CorporateCustomersFixExternalIds(customers []IdentifiersPair) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -857,7 +914,7 @@ func (c *Client) CorporateCustomersFixExternalIds(customers []IdentifiersPair) (
 	customersJSON, _ := json.Marshal(&customers)
 
 	p := url.Values{
-		"customersCorporate": {string(customersJSON[:])},
+		"customersCorporate": {string(customersJSON)},
 	}
 
 	data, status, err := c.PostRequest("/customers-corporate/fix-external-ids", p)
@@ -865,7 +922,10 @@ func (c *Client) CorporateCustomersFixExternalIds(customers []IdentifiersPair) (
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -876,24 +936,24 @@ func (c *Client) CorporateCustomersFixExternalIds(customers []IdentifiersPair) (
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomersHistory(v5.CorporateCustomersHistoryRequest{
-//		Filter: v5.CorporateCustomersHistoryFilter{
+// 	data, status, err := client.CorporateCustomersHistory(retailcrm.CorporateCustomersHistoryRequest{
+//		Filter: retailcrm.CorporateCustomersHistoryFilter{
 //			SinceID: 20,
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.History {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) CorporateCustomersHistory(parameters CorporateCustomersHistoryRequest) (
 	CorporateCustomersHistoryResponse, int, error,
@@ -907,20 +967,23 @@ func (c *Client) CorporateCustomersHistory(parameters CorporateCustomersHistoryR
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
 
-// CorporateCustomers returns list of corporate customers matched the specified filter
+// CorporateCustomersNotes returns list of corporate customers notes matched the specified filter
 //
 // For more information see http://help.retailcrm.pro/Developers/ApiVersion5#get--api-v5-customers-corporate-notes
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomersNotes(v5.CorporateCustomersNotesRequest{
+// 	data, status, err := client.CorporateCustomersNotes(retailcrm.CorporateCustomersNotesRequest{
 //		Filter: CorporateCustomersNotesFilter{
 //			Text: "text",
 //		},
@@ -928,15 +991,15 @@ func (c *Client) CorporateCustomersHistory(parameters CorporateCustomersHistoryR
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.Notes {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) CorporateCustomersNotes(parameters CorporateCustomersNotesRequest) (
 	CorporateCustomersNotesResponse, int, error,
@@ -950,7 +1013,10 @@ func (c *Client) CorporateCustomersNotes(parameters CorporateCustomersNotesReque
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -961,25 +1027,25 @@ func (c *Client) CorporateCustomersNotes(parameters CorporateCustomersNotesReque
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomerNoteCreate(v5.CorporateCustomerNote{
+// 	data, status, err := client.CorporateCustomerNoteCreate(retailcrm.CorporateCustomerNote{
 //		Text:  "text",
-//      Customer: &v5.IdentifiersPair{
+//      Customer: &retailcrm.IdentifiersPair{
 //			ID: 1,
 //		}
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-//		fmt.Printf("%v", err.Id)
+//		fmt.Printf("%v", data.ID)
 //	}
 func (c *Client) CorporateCustomerNoteCreate(note CorporateCustomerNote, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -987,7 +1053,7 @@ func (c *Client) CorporateCustomerNoteCreate(note CorporateCustomerNote, site ..
 	noteJSON, _ := json.Marshal(&note)
 
 	p := url.Values{
-		"note": {string(noteJSON[:])},
+		"note": {string(noteJSON)},
 	}
 
 	fillSite(&p, site)
@@ -997,7 +1063,10 @@ func (c *Client) CorporateCustomerNoteCreate(note CorporateCustomerNote, site ..
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1008,16 +1077,16 @@ func (c *Client) CorporateCustomerNoteCreate(note CorporateCustomerNote, site ..
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.CorporateCustomerNoteDelete(12)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CorporateCustomerNoteDelete(id int) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -1031,7 +1100,10 @@ func (c *Client) CorporateCustomerNoteDelete(id int) (SuccessfulResponse, int, e
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1042,9 +1114,9 @@ func (c *Client) CorporateCustomerNoteDelete(id int) (SuccessfulResponse, int, e
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomersUpload([]v5.CorporateCustomer{
+// 	data, status, err := client.CorporateCustomersUpload([]retailcrm.CorporateCustomer{
 //		{
 //			Nickname:  "Company",
 //			ExternalID: 1,
@@ -1056,15 +1128,15 @@ func (c *Client) CorporateCustomerNoteDelete(id int) (SuccessfulResponse, int, e
 //	}}
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.UploadedCustomers)
+// 		log.Printf("%v\n", data.UploadedCustomers)
 // 	}
 func (c *Client) CorporateCustomersUpload(
 	customers []CorporateCustomer, site ...string,
@@ -1074,7 +1146,7 @@ func (c *Client) CorporateCustomersUpload(
 	uploadJSON, _ := json.Marshal(&customers)
 
 	p := url.Values{
-		"customersCorporate": {string(uploadJSON[:])},
+		"customersCorporate": {string(uploadJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1084,7 +1156,10 @@ func (c *Client) CorporateCustomersUpload(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1095,20 +1170,20 @@ func (c *Client) CorporateCustomersUpload(
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomer(12, v5.ByExternalID, "")
+// 	data, status, err := client.CorporateCustomer(12, retailcrm.ByExternalID, "")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.CorporateCustomer)
+// 		log.Printf("%v\n", data.CorporateCustomer)
 // 	}
 func (c *Client) CorporateCustomer(id, by, site string) (CorporateCustomerResponse, int, error) {
 	var resp CorporateCustomerResponse
@@ -1122,7 +1197,10 @@ func (c *Client) CorporateCustomer(id, by, site string) (CorporateCustomerRespon
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1133,28 +1211,28 @@ func (c *Client) CorporateCustomer(id, by, site string) (CorporateCustomerRespon
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomerAddresses("ext-id", v5.CorporateCustomerAddressesRequest{
+// 	data, status, err := client.CorporateCustomerAddresses("ext-id", retailcrm.CorporateCustomerAddressesRequest{
 // 		Filter: v5,CorporateCustomerAddressesFilter{
 // 			Name: "Main Address",
 // 		},
-// 		By:    v5.ByExternalID,
+// 		By:    retailcrm.ByExternalID,
 // 		Site:  "site",
 // 		Limit: 20,
 // 		Page:  1,
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Addresses)
+// 		log.Printf("%v\n", data.Addresses)
 // 	}
 func (c *Client) CorporateCustomerAddresses(
 	id string, parameters CorporateCustomerAddressesRequest,
@@ -1169,7 +1247,10 @@ func (c *Client) CorporateCustomerAddresses(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1180,19 +1261,19 @@ func (c *Client) CorporateCustomerAddresses(
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := c.CorporateCustomerAddressesCreate("ext-id", v5.ByExternalID, v5.CorporateCustomerAddress{
+// 	data, status, err := c.CorporateCustomerAddressesCreate("ext-id", retailcrm.ByExternalID, retailcrm.CorporateCustomerAddress{
 // 		Text: "this is new address",
 // 		Name: "New Address",
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
@@ -1206,8 +1287,8 @@ func (c *Client) CorporateCustomerAddressesCreate(
 	addressJSON, _ := json.Marshal(&address)
 
 	p := url.Values{
-		"address": {string(addressJSON[:])},
-		"by":      {string(checkBy(by))},
+		"address": {string(addressJSON)},
+		"by":      {checkBy(by)},
 	}
 
 	fillSite(&p, site)
@@ -1217,23 +1298,26 @@ func (c *Client) CorporateCustomerAddressesCreate(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
 
-// CorporateCustomersAddressesEdit edit exact corporate customer address
+// CorporateCustomerAddressesEdit edit exact corporate customer address
 //
 // For more information see http://help.retailcrm.pro/Developers/ApiVersion5#post--api-v5-customers-corporate-externalId-addresses-entityExternalId-edit
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := c.CorporateCustomerAddressesEdit(
 // 		"customer-ext-id",
-// 		v5.ByExternalID,
-// 		v5.ByExternalID,
+// 		retailcrm.ByExternalID,
+// 		retailcrm.ByExternalID,
 // 		CorporateCustomerAddress{
 // 			ExternalID: "addr-ext-id",
 // 			Name:       "Main Address 2",
@@ -1241,15 +1325,15 @@ func (c *Client) CorporateCustomerAddressesCreate(
 // 	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Customer)
+// 		log.Printf("%v\n", data.Customer)
 // 	}
 func (c *Client) CorporateCustomerAddressesEdit(
 	customerID, customerBy, entityBy string, address CorporateCustomerAddress, site ...string,
@@ -1263,18 +1347,18 @@ func (c *Client) CorporateCustomerAddressesEdit(
 	entityBy = checkBy(entityBy)
 
 	switch entityBy {
-	case "id":
+	case ByID:
 		uid = strconv.Itoa(address.ID)
-	case "externalId":
+	case ByExternalID:
 		uid = address.ExternalID
 	}
 
 	addressJSON, _ := json.Marshal(&address)
 
 	p := url.Values{
-		"by":       {string(customerBy)},
-		"entityBy": {string(entityBy)},
-		"address":  {string(addressJSON[:])},
+		"by":       {customerBy},
+		"entityBy": {entityBy},
+		"address":  {string(addressJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1284,7 +1368,10 @@ func (c *Client) CorporateCustomerAddressesEdit(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1295,28 +1382,28 @@ func (c *Client) CorporateCustomerAddressesEdit(
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomerCompanies("ext-id", v5.IdentifiersPairRequest{
+// 	data, status, err := client.CorporateCustomerCompanies("ext-id", retailcrm.IdentifiersPairRequest{
 // 		Filter: v5,IdentifiersPairFilter{
 // 			Ids: []string{"1"},
 // 		},
-// 		By:    v5.ByExternalID,
+// 		By:    retailcrm.ByExternalID,
 // 		Site:  "site",
 // 		Limit: 20,
 // 		Page:  1,
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Companies)
+// 		log.Printf("%v\n", data.Companies)
 // 	}
 func (c *Client) CorporateCustomerCompanies(
 	id string, parameters IdentifiersPairRequest,
@@ -1331,7 +1418,10 @@ func (c *Client) CorporateCustomerCompanies(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1342,18 +1432,18 @@ func (c *Client) CorporateCustomerCompanies(
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := c.CorporateCustomerCompaniesCreate("ext-id", v5.ByExternalID, v5.Company{
+// 	data, status, err := c.CorporateCustomerCompaniesCreate("ext-id", retailcrm.ByExternalID, retailcrm.Company{
 // 		Name: "Company name",
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
@@ -1367,8 +1457,8 @@ func (c *Client) CorporateCustomerCompaniesCreate(
 	companyJSON, _ := json.Marshal(&company)
 
 	p := url.Values{
-		"company": {string(companyJSON[:])},
-		"by":      {string(checkBy(by))},
+		"company": {string(companyJSON)},
+		"by":      {checkBy(by)},
 	}
 
 	fillSite(&p, site)
@@ -1378,7 +1468,10 @@ func (c *Client) CorporateCustomerCompaniesCreate(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1389,12 +1482,12 @@ func (c *Client) CorporateCustomerCompaniesCreate(
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := c.CorporateCustomerCompaniesEdit(
 // 		"customer-ext-id",
-// 		v5.ByExternalID,
-// 		v5.ByExternalID,
+// 		retailcrm.ByExternalID,
+// 		retailcrm.ByExternalID,
 // 		Company{
 // 			ExternalID: "company-ext-id",
 // 			Name:       "New Company Name",
@@ -1402,15 +1495,15 @@ func (c *Client) CorporateCustomerCompaniesCreate(
 // 	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) CorporateCustomerCompaniesEdit(
 	customerID, customerBy, entityBy string, company Company, site ...string,
@@ -1424,18 +1517,18 @@ func (c *Client) CorporateCustomerCompaniesEdit(
 	entityBy = checkBy(entityBy)
 
 	switch entityBy {
-	case "id":
+	case ByID:
 		uid = strconv.Itoa(company.ID)
-	case "externalId":
+	case ByExternalID:
 		uid = company.ExternalID
 	}
 
 	addressJSON, _ := json.Marshal(&company)
 
 	p := url.Values{
-		"by":       {string(customerBy)},
-		"entityBy": {string(entityBy)},
-		"company":  {string(addressJSON[:])},
+		"by":       {customerBy},
+		"entityBy": {entityBy},
+		"company":  {string(addressJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1445,7 +1538,10 @@ func (c *Client) CorporateCustomerCompaniesEdit(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1456,28 +1552,28 @@ func (c *Client) CorporateCustomerCompaniesEdit(
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CorporateCustomerContacts("ext-id", v5.IdentifiersPairRequest{
-// 		Filter: v5.IdentifiersPairFilter{
+// 	data, status, err := client.CorporateCustomerContacts("ext-id", retailcrm.IdentifiersPairRequest{
+// 		Filter: retailcrm.IdentifiersPairFilter{
 // 			Ids: []string{"1"},
 // 		},
-// 		By:    v5.ByExternalID,
+// 		By:    retailcrm.ByExternalID,
 // 		Site:  "site",
 // 		Limit: 20,
 // 		Page:  1,
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Contacts)
+// 		log.Printf("%v\n", data.Contacts)
 // 	}
 func (c *Client) CorporateCustomerContacts(
 	id string, parameters IdentifiersPairRequest,
@@ -1492,7 +1588,10 @@ func (c *Client) CorporateCustomerContacts(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1503,11 +1602,11 @@ func (c *Client) CorporateCustomerContacts(
 //
 // Example (customer with specified id or externalId should exist in specified site):
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := c.CorporateCustomerContactsCreate("ext-id", v5.ByExternalID, v5.CorporateCustomerContact{
+// 	data, status, err := c.CorporateCustomerContactsCreate("ext-id", retailcrm.ByExternalID, retailcrm.CorporateCustomerContact{
 // 		IsMain: false,
-// 		Customer: v5.CorporateCustomerContactCustomer{
+// 		Customer: retailcrm.CorporateCustomerContactCustomer{
 // 			ExternalID: "external_id",
 // 			Site:       "site",
 // 		},
@@ -1515,11 +1614,11 @@ func (c *Client) CorporateCustomerContacts(
 // 	}, "site")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
@@ -1533,8 +1632,8 @@ func (c *Client) CorporateCustomerContactsCreate(
 	companyJSON, _ := json.Marshal(&contact)
 
 	p := url.Values{
-		"contact": {string(companyJSON[:])},
-		"by":      {string(checkBy(by))},
+		"contact": {string(companyJSON)},
+		"by":      {checkBy(by)},
 	}
 
 	fillSite(&p, site)
@@ -1544,7 +1643,10 @@ func (c *Client) CorporateCustomerContactsCreate(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1555,25 +1657,25 @@ func (c *Client) CorporateCustomerContactsCreate(
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := c.CorporateCustomerContactsEdit("ext-id", v5.ByExternalID, v5.ByID, v5.CorporateCustomerContact{
+// 	data, status, err := c.CorporateCustomerContactsEdit("ext-id", retailcrm.ByExternalID, retailcrm.ByID, retailcrm.CorporateCustomerContact{
 // 		IsMain: false,
-// 		Customer: v5.CorporateCustomerContactCustomer{
+// 		Customer: retailcrm.CorporateCustomerContactCustomer{
 // 			ID: 2350,
 // 		},
 // 	}, "site")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) CorporateCustomerContactsEdit(
 	customerID, customerBy, entityBy string, contact CorporateCustomerContact, site ...string,
@@ -1587,18 +1689,18 @@ func (c *Client) CorporateCustomerContactsEdit(
 	entityBy = checkBy(entityBy)
 
 	switch entityBy {
-	case "id":
+	case ByID:
 		uid = strconv.Itoa(contact.Customer.ID)
-	case "externalId":
+	case ByExternalID:
 		uid = contact.Customer.ExternalID
 	}
 
 	addressJSON, _ := json.Marshal(&contact)
 
 	p := url.Values{
-		"by":       {string(customerBy)},
-		"entityBy": {string(entityBy)},
-		"contact":  {string(addressJSON[:])},
+		"by":       {customerBy},
+		"entityBy": {entityBy},
+		"contact":  {string(addressJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1608,7 +1710,10 @@ func (c *Client) CorporateCustomerContactsEdit(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1619,29 +1724,29 @@ func (c *Client) CorporateCustomerContactsEdit(
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CorporateCustomerEdit(
-//		v5.CorporateCustomer{
+//		retailcrm.CorporateCustomer{
 //			FirstName:  "Ivan",
 //			LastName:   "Ivanov",
 //			Patronymic: "Ivanovich",
 //			ID: 		1,
 //			Email:      "ivanov@example.com",
 //		},
-//		v5.ByID,
+//		retailcrm.ByID,
 //	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Customer)
+// 		log.Printf("%v\n", data.Customer)
 // 	}
 func (c *Client) CorporateCustomerEdit(customer CorporateCustomer, by string, site ...string) (
 	CustomerChangeResponse, int, error,
@@ -1657,8 +1762,8 @@ func (c *Client) CorporateCustomerEdit(customer CorporateCustomer, by string, si
 	customerJSON, _ := json.Marshal(&customer)
 
 	p := url.Values{
-		"by":                {string(context)},
-		"customerCorporate": {string(customerJSON[:])},
+		"by":                {context},
+		"customerCorporate": {string(customerJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1668,7 +1773,10 @@ func (c *Client) CorporateCustomerEdit(customer CorporateCustomer, by string, si
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1679,14 +1787,14 @@ func (c *Client) CorporateCustomerEdit(customer CorporateCustomer, by string, si
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //  t, _ := time.Parse("2006-01-02 15:04:05", "2012-12-12 12:12:12")
 //
 //	data, status, err := client.DeliveryTracking(
-//		[]v5.DeliveryTrackingRequest{{
+//		[]retailcrm.DeliveryTrackingRequest{{
 //			DeliveryID: "1",
 //			TrackNumber: "123",
-//			History: []v5.DeliveryHistoryRecord{
+//			History: []retailcrm.DeliveryHistoryRecord{
 //				{
 //					Code: "cancel",
 //					UpdatedAt: t.Format(time.RFC3339),
@@ -1697,11 +1805,11 @@ func (c *Client) CorporateCustomerEdit(customer CorporateCustomer, by string, si
 //	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 func (c *Client) DeliveryTracking(parameters []DeliveryTrackingRequest, subcode string) (
@@ -1712,7 +1820,7 @@ func (c *Client) DeliveryTracking(parameters []DeliveryTrackingRequest, subcode
 	updateJSON, _ := json.Marshal(&parameters)
 
 	p := url.Values{
-		"statusUpdate": {string(updateJSON[:])},
+		"statusUpdate": {string(updateJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/delivery/generic/%s/tracking", subcode), p)
@@ -1720,7 +1828,10 @@ func (c *Client) DeliveryTracking(parameters []DeliveryTrackingRequest, subcode
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1731,25 +1842,25 @@ func (c *Client) DeliveryTracking(parameters []DeliveryTrackingRequest, subcode
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.DeliveryShipments(v5.DeliveryShipmentsRequest{
+// 	data, status, err := client.DeliveryShipments(retailcrm.DeliveryShipmentsRequest{
 //		Limit: 12,
-//		Filter: v5.ShipmentFilter{
+//		Filter: retailcrm.ShipmentFilter{
 //			DateFrom: "2012-12-12",
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.DeliveryShipments {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (DeliveryShipmentsResponse, int, error) {
 	var resp DeliveryShipmentsResponse
@@ -1761,7 +1872,10 @@ func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (Deliver
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1772,30 +1886,30 @@ func (c *Client) DeliveryShipments(parameters DeliveryShipmentsRequest) (Deliver
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.DeliveryShipmentCreate(
-//		v5.DeliveryShipment{
+//		retailcrm.DeliveryShipment{
 //			Date: "2012-12-12",
-//			Time: v5.DeliveryTime{
+//			Time: retailcrm.DeliveryTime{
 //				From: "18:00",
 //				To: "20:00",
 //			},
-//			Orders: []v5.Order{{Number: "12"}},
+//			Orders: []retailcrm.Order{{Number: "12"}},
 //		},
 //		"sdek",
 //	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) DeliveryShipmentCreate(
 	shipment DeliveryShipment, deliveryType string, site ...string,
@@ -1804,8 +1918,8 @@ func (c *Client) DeliveryShipmentCreate(
 	updateJSON, _ := json.Marshal(&shipment)
 
 	p := url.Values{
-		"deliveryType":     {string(deliveryType)},
-		"deliveryShipment": {string(updateJSON[:])},
+		"deliveryType":     {deliveryType},
+		"deliveryShipment": {string(updateJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1815,7 +1929,10 @@ func (c *Client) DeliveryShipmentCreate(
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1826,20 +1943,20 @@ func (c *Client) DeliveryShipmentCreate(
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.DeliveryShipment(12)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.DeliveryShipment)
+// 		log.Printf("%v\n", data.DeliveryShipment)
 // 	}
 func (c *Client) DeliveryShipment(id int) (DeliveryShipmentResponse, int, error) {
 	var resp DeliveryShipmentResponse
@@ -1849,7 +1966,10 @@ func (c *Client) DeliveryShipment(id int) (DeliveryShipmentResponse, int, error)
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1860,22 +1980,22 @@ func (c *Client) DeliveryShipment(id int) (DeliveryShipmentResponse, int, error)
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.DeliveryShipmentEdit(v5.DeliveryShipment{
+// 	data, status, err := client.DeliveryShipmentEdit(retailcrm.DeliveryShipment{
 //		ID: "12",
-//		Time: v5.DeliveryTime{
+//		Time: retailcrm.DeliveryTime{
 //			From: "14:00",
 //			To: "18:00",
 //		},
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string) (
 	DeliveryShipmentUpdateResponse, int, error,
@@ -1884,7 +2004,7 @@ func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string)
 	updateJSON, _ := json.Marshal(&shipment)
 
 	p := url.Values{
-		"deliveryShipment": {string(updateJSON[:])},
+		"deliveryShipment": {string(updateJSON)},
 	}
 
 	fillSite(&p, site)
@@ -1894,7 +2014,10 @@ func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string)
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1905,20 +2028,20 @@ func (c *Client) DeliveryShipmentEdit(shipment DeliveryShipment, site ...string)
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.IntegrationModule("moysklad3")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.IntegrationModule)
+// 		log.Printf("%v\n", data.IntegrationModule)
 // 	}
 func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int, error) {
 	var resp IntegrationModuleResponse
@@ -1928,7 +2051,10 @@ func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int,
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1939,12 +2065,12 @@ func (c *Client) IntegrationModule(code string) (IntegrationModuleResponse, int,
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	name := "MS"
 //	code := "moysklad3"
 //
-//	data, status, err := client.IntegrationModuleEdit(v5.IntegrationModule{
+//	data, status, err := client.IntegrationModuleEdit(retailcrm.IntegrationModule{
 //		Code:            code,
 //		IntegrationCode: code,
 //		Active:          false,
@@ -1972,14 +2098,17 @@ func (c *Client) IntegrationModuleEdit(integrationModule IntegrationModule) (
 	var resp IntegrationModuleEditResponse
 	updateJSON, _ := json.Marshal(&integrationModule)
 
-	p := url.Values{"integrationModule": {string(updateJSON[:])}}
+	p := url.Values{"integrationModule": {string(updateJSON)}}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/integration-modules/%s/edit", integrationModule.Code), p)
 	if err != nil {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -1990,20 +2119,20 @@ func (c *Client) IntegrationModuleEdit(integrationModule IntegrationModule) (
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Orders(v5.OrdersRequest{Filter: v5.OrdersFilter{City: "Moscow"}, Page: 1})
+// 	data, status, err := client.Orders(retailcrm.OrdersRequest{Filter: retailcrm.OrdersFilter{City: "Moscow"}, Page: 1})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.Orders {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Orders(parameters OrdersRequest) (OrdersResponse, int, error) {
 	var resp OrdersResponse
@@ -2015,7 +2144,10 @@ func (c *Client) Orders(parameters OrdersRequest) (OrdersResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2026,16 +2158,16 @@ func (c *Client) Orders(parameters OrdersRequest) (OrdersResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrdersCombine("ours", v5.Order{ID: 1}, v5.Order{ID: 1})
+// 	data, status, err := client.OrdersCombine("ours", retailcrm.Order{ID: 1}, retailcrm.Order{ID: 1})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (OperationResponse, int, error) {
 	var resp OperationResponse
@@ -2045,8 +2177,8 @@ func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (Oper
 
 	p := url.Values{
 		"technique":   {technique},
-		"order":       {string(combineJSONIn[:])},
-		"resultOrder": {string(combineJSONOut[:])},
+		"order":       {string(combineJSONIn)},
+		"resultOrder": {string(combineJSONOut)},
 	}
 
 	data, status, err := c.PostRequest("/orders/combine", p)
@@ -2054,7 +2186,10 @@ func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (Oper
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2065,33 +2200,33 @@ func (c *Client) OrdersCombine(technique string, order, resultOrder Order) (Oper
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrderCreate(v5.Order{
+// 	data, status, err := client.OrderCreate(retailcrm.Order{
 //		FirstName:  "Ivan",
 //		LastName:   "Ivanov",
 //		Patronymic: "Ivanovich",
 //		Email:      "ivanov@example.com",
-//		Items:      []v5.OrderItem{{Offer: v5.Offer{ID: 12}, Quantity: 5}},
+//		Items:      []retailcrm.OrderItem{{Offer: retailcrm.Offer{ID: 12}, Quantity: 5}},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) OrderCreate(order Order, site ...string) (OrderCreateResponse, int, error) {
 	var resp OrderCreateResponse
 	orderJSON, _ := json.Marshal(&order)
 
 	p := url.Values{
-		"order": {string(orderJSON[:])},
+		"order": {string(orderJSON)},
 	}
 
 	fillSite(&p, site)
@@ -2101,7 +2236,10 @@ func (c *Client) OrderCreate(order Order, site ...string) (OrderCreateResponse,
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2112,9 +2250,9 @@ func (c *Client) OrderCreate(order Order, site ...string) (OrderCreateResponse,
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.OrdersFixExternalIds(([]v5.IdentifiersPair{{
+//	data, status, err := client.OrdersFixExternalIds(([]retailcrm.IdentifiersPair{{
 //		ID:         1,
 //		ExternalID: 12,
 //	}})
@@ -2136,7 +2274,7 @@ func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulRespo
 	ordersJSON, _ := json.Marshal(&orders)
 
 	p := url.Values{
-		"orders": {string(ordersJSON[:])},
+		"orders": {string(ordersJSON)},
 	}
 
 	data, status, err := c.PostRequest("/orders/fix-external-ids", p)
@@ -2144,7 +2282,10 @@ func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulRespo
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2155,20 +2296,20 @@ func (c *Client) OrdersFixExternalIds(orders []IdentifiersPair) (SuccessfulRespo
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrdersHistory(v5.OrdersHistoryRequest{Filter: v5.OrdersHistoryFilter{SinceID: 20}})
+// 	data, status, err := client.OrdersHistory(retailcrm.OrdersHistoryRequest{Filter: retailcrm.OrdersHistoryFilter{SinceID: 20}})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.History {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (OrdersHistoryResponse, int, error) {
 	var resp OrdersHistoryResponse
@@ -2180,7 +2321,10 @@ func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (OrdersHistoryRe
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2191,10 +2335,10 @@ func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (OrdersHistoryRe
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrderPaymentCreate(v5.Payment{
-//		Order: &v5.Order{
+// 	data, status, err := client.OrderPaymentCreate(retailcrm.Payment{
+//		Order: &retailcrm.Order{
 //			ID: 12,
 //		},
 //		Amount: 300,
@@ -2202,15 +2346,15 @@ func (c *Client) OrdersHistory(parameters OrdersHistoryRequest) (OrdersHistoryRe
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -2218,7 +2362,7 @@ func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResp
 	paymentJSON, _ := json.Marshal(&payment)
 
 	p := url.Values{
-		"payment": {string(paymentJSON[:])},
+		"payment": {string(paymentJSON)},
 	}
 
 	fillSite(&p, site)
@@ -2228,7 +2372,10 @@ func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResp
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2239,16 +2386,16 @@ func (c *Client) OrderPaymentCreate(payment Payment, site ...string) (CreateResp
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.OrderPaymentDelete(12)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2262,7 +2409,10 @@ func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2273,22 +2423,22 @@ func (c *Client) OrderPaymentDelete(id int) (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.OrderPaymentEdit(
-// 		v5.Payment{
+// 		retailcrm.Payment{
 //			ID:     12,
 //			Amount: 500,
 //		},
-//		v5.ByID,
+//		retailcrm.ByID,
 //	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2303,7 +2453,7 @@ func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (S
 
 	p := url.Values{
 		"by":      {context},
-		"payment": {string(paymentJSON[:])},
+		"payment": {string(paymentJSON)},
 	}
 
 	fillSite(&p, site)
@@ -2313,7 +2463,10 @@ func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (S
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2324,19 +2477,19 @@ func (c *Client) OrderPaymentEdit(payment Payment, by string, site ...string) (S
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrdersStatuses(v5.OrdersStatusesRequest{
+// 	data, status, err := client.OrdersStatuses(retailcrm.OrdersStatusesRequest{
 //		IDs:         []int{1},
 //		ExternalIDs: []string{"2"},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrdersStatuses(request OrdersStatusesRequest) (OrdersStatusesResponse, int, error) {
 	var resp OrdersStatusesResponse
@@ -2348,7 +2501,10 @@ func (c *Client) OrdersStatuses(request OrdersStatusesRequest) (OrdersStatusesRe
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2359,35 +2515,35 @@ func (c *Client) OrdersStatuses(request OrdersStatusesRequest) (OrdersStatusesRe
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrdersUpload([]v5.Order{
+// 	data, status, err := client.OrdersUpload([]retailcrm.Order{
 //		{
 //			FirstName:  "Ivan",
 //			LastName:   "Ivanov",
 //			Patronymic: "Ivanovich",
 //			Email:      "ivanov@example.com",
-//			Items:      []v5.OrderItem{{Offer: v5.Offer{ID: 12}, Quantity: 5}},
+//			Items:      []retailcrm.OrderItem{{Offer: retailcrm.Offer{ID: 12}, Quantity: 5}},
 //		},
 //		{
 //			FirstName:  "Pert",
 //			LastName:   "Petrov",
 //			Patronymic: "Petrovich",
 //			Email:      "petrov@example.com",
-//			Items:      []v5.OrderItem{{Offer: v5.Offer{ID: 13}, Quantity: 1}},
+//			Items:      []retailcrm.OrderItem{{Offer: retailcrm.Offer{ID: 13}, Quantity: 1}},
 //		}
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.UploadedOrders)
+// 		log.Printf("%v\n", data.UploadedOrders)
 // 	}
 func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadResponse, int, error) {
 	var resp OrdersUploadResponse
@@ -2395,7 +2551,7 @@ func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadRespo
 	uploadJSON, _ := json.Marshal(&orders)
 
 	p := url.Values{
-		"orders": {string(uploadJSON[:])},
+		"orders": {string(uploadJSON)},
 	}
 
 	fillSite(&p, site)
@@ -2405,7 +2561,10 @@ func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadRespo
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2416,20 +2575,20 @@ func (c *Client) OrdersUpload(orders []Order, site ...string) (OrdersUploadRespo
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Order(12, v5.ByExternalID, "")
+// 	data, status, err := client.Order(12, retailcrm.ByExternalID, "")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Order)
+// 		log.Printf("%v\n", data.Order)
 // 	}
 func (c *Client) Order(id, by, site string) (OrderResponse, int, error) {
 	var resp OrderResponse
@@ -2443,7 +2602,10 @@ func (c *Client) Order(id, by, site string) (OrderResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2454,22 +2616,22 @@ func (c *Client) Order(id, by, site string) (OrderResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.OrderEdit(
-// 		v5.Order{
+// 		retailcrm.Order{
 //			ID:    12,
-//			Items: []v5.OrderItem{{Offer: v5.Offer{ID: 13}, Quantity: 6}},
+//			Items: []retailcrm.OrderItem{{Offer: retailcrm.Offer{ID: 13}, Quantity: 6}},
 //		},
-// 		v5.ByID,
+// 		retailcrm.ByID,
 // 	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -2483,8 +2645,8 @@ func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateRespon
 	orderJSON, _ := json.Marshal(&order)
 
 	p := url.Values{
-		"by":    {string(context)},
-		"order": {string(orderJSON[:])},
+		"by":    {context},
+		"order": {string(orderJSON)},
 	}
 
 	fillSite(&p, site)
@@ -2494,7 +2656,10 @@ func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateRespon
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2505,20 +2670,20 @@ func (c *Client) OrderEdit(order Order, by string, site ...string) (CreateRespon
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Packs(v5.PacksRequest{Filter: v5.PacksFilter{OrderID: 12}})
+// 	data, status, err := client.Packs(retailcrm.PacksRequest{Filter: retailcrm.PacksFilter{OrderID: 12}})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Packs {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, error) {
 	var resp PacksResponse
@@ -2530,7 +2695,10 @@ func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2541,7 +2709,7 @@ func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.PackCreate(Pack{
 //		Store:    "store-1",
@@ -2550,22 +2718,22 @@ func (c *Client) Packs(parameters PacksRequest) (PacksResponse, int, error) {
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) PackCreate(pack Pack) (CreateResponse, int, error) {
 	var resp CreateResponse
 	packJSON, _ := json.Marshal(&pack)
 
 	p := url.Values{
-		"pack": {string(packJSON[:])},
+		"pack": {string(packJSON)},
 	}
 
 	data, status, err := c.PostRequest("/orders/packs/create", p)
@@ -2573,7 +2741,10 @@ func (c *Client) PackCreate(pack Pack) (CreateResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2584,20 +2755,20 @@ func (c *Client) PackCreate(pack Pack) (CreateResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.PacksHistory(v5.PacksHistoryRequest{Filter: v5.OrdersHistoryFilter{SinceID: 5}})
+// 	data, status, err := client.PacksHistory(retailcrm.PacksHistoryRequest{Filter: retailcrm.OrdersHistoryFilter{SinceID: 5}})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.History {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryResponse, int, error) {
 	var resp PacksHistoryResponse
@@ -2609,7 +2780,10 @@ func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryRespo
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2620,20 +2794,20 @@ func (c *Client) PacksHistory(parameters PacksHistoryRequest) (PacksHistoryRespo
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.Pack(112)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Pack)
+// 		log.Printf("%v\n", data.Pack)
 // 	}
 func (c *Client) Pack(id int) (PackResponse, int, error) {
 	var resp PackResponse
@@ -2643,7 +2817,10 @@ func (c *Client) Pack(id int) (PackResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2654,16 +2831,16 @@ func (c *Client) Pack(id int) (PackResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.PackDelete(112)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) PackDelete(id int) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2673,7 +2850,10 @@ func (c *Client) PackDelete(id int) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2684,16 +2864,16 @@ func (c *Client) PackDelete(id int) (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.PackEdit(Pack{ID: 12, Quantity: 2})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) PackEdit(pack Pack) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -2701,7 +2881,7 @@ func (c *Client) PackEdit(pack Pack) (CreateResponse, int, error) {
 	packJSON, _ := json.Marshal(&pack)
 
 	p := url.Values{
-		"pack": {string(packJSON[:])},
+		"pack": {string(packJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/orders/packs/%d/edit", pack.ID), p)
@@ -2709,7 +2889,10 @@ func (c *Client) PackEdit(pack Pack) (CreateResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2725,7 +2908,10 @@ func (c *Client) Countries() (CountriesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2741,7 +2927,10 @@ func (c *Client) CostGroups() (CostGroupsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2752,19 +2941,19 @@ func (c *Client) CostGroups() (CostGroupsResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CostGroupEdit(v5.CostGroup{
+// 	data, status, err := client.CostGroupEdit(retailcrm.CostGroup{
 //		Code:   "group-1",
 //		Color:  "#da5c98",
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CostGroupEdit(costGroup CostGroup) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2772,7 +2961,7 @@ func (c *Client) CostGroupEdit(costGroup CostGroup) (SuccessfulResponse, int, er
 	objJSON, _ := json.Marshal(&costGroup)
 
 	p := url.Values{
-		"costGroup": {string(objJSON[:])},
+		"costGroup": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/cost-groups/%s/edit", costGroup.Code), p)
@@ -2780,7 +2969,10 @@ func (c *Client) CostGroupEdit(costGroup CostGroup) (SuccessfulResponse, int, er
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2796,7 +2988,10 @@ func (c *Client) CostItems() (CostItemsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2807,19 +3002,19 @@ func (c *Client) CostItems() (CostItemsResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CostItemEdit(v5.CostItem{
+// 	data, status, err := client.CostItemEdit(retailcrm.CostItem{
 //		Code:            "seo",
 //		Active:          false,
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CostItemEdit(costItem CostItem) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2827,7 +3022,7 @@ func (c *Client) CostItemEdit(costItem CostItem) (SuccessfulResponse, int, error
 	objJSON, _ := json.Marshal(&costItem)
 
 	p := url.Values{
-		"costItem": {string(objJSON[:])},
+		"costItem": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/cost-items/%s/edit", costItem.Code), p)
@@ -2835,7 +3030,10 @@ func (c *Client) CostItemEdit(costItem CostItem) (SuccessfulResponse, int, error
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2851,7 +3049,10 @@ func (c *Client) Couriers() (CouriersResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2862,9 +3063,9 @@ func (c *Client) Couriers() (CouriersResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CostItemEdit(v5.Courier{
+// 	data, status, err := client.CostItemEdit(retailcrm.Courier{
 //		Active:    true,
 //		Email:     "courier1@example.com",
 //		FirstName: "Ivan",
@@ -2872,15 +3073,15 @@ func (c *Client) Couriers() (CouriersResponse, int, error) {
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	if data.Success == true {
-// 		fmt.Printf("%v", data.ID)
+// 		log.Printf("%v", data.ID)
 // 	}
 func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -2888,7 +3089,7 @@ func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, error) {
 	objJSON, _ := json.Marshal(&courier)
 
 	p := url.Values{
-		"courier": {string(objJSON[:])},
+		"courier": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest("/reference/couriers/create", p)
@@ -2896,7 +3097,10 @@ func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2907,19 +3111,19 @@ func (c *Client) CourierCreate(courier Courier) (CreateResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.CostItemEdit(v5.Courier{
+// 	data, status, err := client.CostItemEdit(retailcrm.Courier{
 //		ID:    	  1,
 //		Patronymic: "Ivanovich",
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CourierEdit(courier Courier) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2927,7 +3131,7 @@ func (c *Client) CourierEdit(courier Courier) (SuccessfulResponse, int, error) {
 	objJSON, _ := json.Marshal(&courier)
 
 	p := url.Values{
-		"courier": {string(objJSON[:])},
+		"courier": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/couriers/%d/edit", courier.ID), p)
@@ -2935,7 +3139,10 @@ func (c *Client) CourierEdit(courier Courier) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2951,7 +3158,10 @@ func (c *Client) DeliveryServices() (DeliveryServiceResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -2962,19 +3172,19 @@ func (c *Client) DeliveryServices() (DeliveryServiceResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.DeliveryServiceEdit(v5.DeliveryService{
+// 	data, status, err := client.DeliveryServiceEdit(retailcrm.DeliveryService{
 //		Active: false,
 //		Code:   "delivery-1",
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) DeliveryServiceEdit(deliveryService DeliveryService) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -2982,7 +3192,7 @@ func (c *Client) DeliveryServiceEdit(deliveryService DeliveryService) (Successfu
 	objJSON, _ := json.Marshal(&deliveryService)
 
 	p := url.Values{
-		"deliveryService": {string(objJSON[:])},
+		"deliveryService": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/delivery-services/%s/edit", deliveryService.Code), p)
@@ -2990,7 +3200,10 @@ func (c *Client) DeliveryServiceEdit(deliveryService DeliveryService) (Successfu
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3006,7 +3219,10 @@ func (c *Client) DeliveryTypes() (DeliveryTypesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3017,9 +3233,9 @@ func (c *Client) DeliveryTypes() (DeliveryTypesResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.DeliveryTypeEdit(v5.DeliveryType{
+// 	data, status, err := client.DeliveryTypeEdit(retailcrm.DeliveryType{
 //		Active:        false,
 //		Code:          "type-1",
 //		DefaultCost:   300,
@@ -3027,11 +3243,11 @@ func (c *Client) DeliveryTypes() (DeliveryTypesResponse, int, error) {
 //	}
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) DeliveryTypeEdit(deliveryType DeliveryType) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -3039,7 +3255,7 @@ func (c *Client) DeliveryTypeEdit(deliveryType DeliveryType) (SuccessfulResponse
 	objJSON, _ := json.Marshal(&deliveryType)
 
 	p := url.Values{
-		"deliveryType": {string(objJSON[:])},
+		"deliveryType": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/delivery-types/%s/edit", deliveryType.Code), p)
@@ -3047,7 +3263,10 @@ func (c *Client) DeliveryTypeEdit(deliveryType DeliveryType) (SuccessfulResponse
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3063,7 +3282,10 @@ func (c *Client) LegalEntities() (LegalEntitiesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3074,19 +3296,19 @@ func (c *Client) LegalEntities() (LegalEntitiesResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.LegalEntityEdit(v5.LegalEntity{
+// 	data, status, err := client.LegalEntityEdit(retailcrm.LegalEntity{
 //		Code:          "legal-entity-1",
 //		CertificateDate:   "2012-12-12",
 //	}
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) LegalEntityEdit(legalEntity LegalEntity) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -3094,7 +3316,7 @@ func (c *Client) LegalEntityEdit(legalEntity LegalEntity) (SuccessfulResponse, i
 	objJSON, _ := json.Marshal(&legalEntity)
 
 	p := url.Values{
-		"legalEntity": {string(objJSON[:])},
+		"legalEntity": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/legal-entities/%s/edit", legalEntity.Code), p)
@@ -3102,7 +3324,10 @@ func (c *Client) LegalEntityEdit(legalEntity LegalEntity) (SuccessfulResponse, i
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3118,7 +3343,10 @@ func (c *Client) OrderMethods() (OrderMethodsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3129,20 +3357,20 @@ func (c *Client) OrderMethods() (OrderMethodsResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrderMethodEdit(v5.OrderMethod{
+// 	data, status, err := client.OrderMethodEdit(retailcrm.OrderMethod{
 //		Code:          "method-1",
 //		Active:        false,
 //		DefaultForCRM: false,
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrderMethodEdit(orderMethod OrderMethod) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -3150,7 +3378,7 @@ func (c *Client) OrderMethodEdit(orderMethod OrderMethod) (SuccessfulResponse, i
 	objJSON, _ := json.Marshal(&orderMethod)
 
 	p := url.Values{
-		"orderMethod": {string(objJSON[:])},
+		"orderMethod": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/order-methods/%s/edit", orderMethod.Code), p)
@@ -3158,7 +3386,10 @@ func (c *Client) OrderMethodEdit(orderMethod OrderMethod) (SuccessfulResponse, i
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3174,7 +3405,10 @@ func (c *Client) OrderTypes() (OrderTypesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3185,20 +3419,20 @@ func (c *Client) OrderTypes() (OrderTypesResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.OrderTypeEdit(v5.OrderType{
+// 	data, status, err := client.OrderTypeEdit(retailcrm.OrderType{
 //		Code:          "order-type-1",
 //		Active:        false,
 //		DefaultForCRM: false,
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) OrderTypeEdit(orderType OrderType) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -3206,7 +3440,7 @@ func (c *Client) OrderTypeEdit(orderType OrderType) (SuccessfulResponse, int, er
 	objJSON, _ := json.Marshal(&orderType)
 
 	p := url.Values{
-		"orderType": {string(objJSON[:])},
+		"orderType": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/order-types/%s/edit", orderType.Code), p)
@@ -3214,7 +3448,10 @@ func (c *Client) OrderTypeEdit(orderType OrderType) (SuccessfulResponse, int, er
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3230,7 +3467,10 @@ func (c *Client) PaymentStatuses() (PaymentStatusesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3244,7 +3484,7 @@ func (c *Client) PaymentStatusEdit(paymentStatus PaymentStatus) (SuccessfulRespo
 	objJSON, _ := json.Marshal(&paymentStatus)
 
 	p := url.Values{
-		"paymentStatus": {string(objJSON[:])},
+		"paymentStatus": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/payment-statuses/%s/edit", paymentStatus.Code), p)
@@ -3252,7 +3492,10 @@ func (c *Client) PaymentStatusEdit(paymentStatus PaymentStatus) (SuccessfulRespo
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3268,7 +3511,10 @@ func (c *Client) PaymentTypes() (PaymentTypesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3282,7 +3528,7 @@ func (c *Client) PaymentTypeEdit(paymentType PaymentType) (SuccessfulResponse, i
 	objJSON, _ := json.Marshal(&paymentType)
 
 	p := url.Values{
-		"paymentType": {string(objJSON[:])},
+		"paymentType": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/payment-types/%s/edit", paymentType.Code), p)
@@ -3290,7 +3536,10 @@ func (c *Client) PaymentTypeEdit(paymentType PaymentType) (SuccessfulResponse, i
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3306,7 +3555,10 @@ func (c *Client) PriceTypes() (PriceTypesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3320,7 +3572,7 @@ func (c *Client) PriceTypeEdit(priceType PriceType) (SuccessfulResponse, int, er
 	objJSON, _ := json.Marshal(&priceType)
 
 	p := url.Values{
-		"priceType": {string(objJSON[:])},
+		"priceType": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/price-types/%s/edit", priceType.Code), p)
@@ -3328,7 +3580,10 @@ func (c *Client) PriceTypeEdit(priceType PriceType) (SuccessfulResponse, int, er
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3344,7 +3599,10 @@ func (c *Client) ProductStatuses() (ProductStatusesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3358,7 +3616,7 @@ func (c *Client) ProductStatusEdit(productStatus ProductStatus) (SuccessfulRespo
 	objJSON, _ := json.Marshal(&productStatus)
 
 	p := url.Values{
-		"productStatus": {string(objJSON[:])},
+		"productStatus": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/product-statuses/%s/edit", productStatus.Code), p)
@@ -3366,7 +3624,10 @@ func (c *Client) ProductStatusEdit(productStatus ProductStatus) (SuccessfulRespo
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3382,7 +3643,10 @@ func (c *Client) Sites() (SitesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3396,7 +3660,7 @@ func (c *Client) SiteEdit(site Site) (SuccessfulResponse, int, error) {
 	objJSON, _ := json.Marshal(&site)
 
 	p := url.Values{
-		"site": {string(objJSON[:])},
+		"site": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/sites/%s/edit", site.Code), p)
@@ -3404,7 +3668,10 @@ func (c *Client) SiteEdit(site Site) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3420,7 +3687,10 @@ func (c *Client) StatusGroups() (StatusGroupsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3436,7 +3706,10 @@ func (c *Client) Statuses() (StatusesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3450,7 +3723,7 @@ func (c *Client) StatusEdit(st Status) (SuccessfulResponse, int, error) {
 	objJSON, _ := json.Marshal(&st)
 
 	p := url.Values{
-		"status": {string(objJSON[:])},
+		"status": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/statuses/%s/edit", st.Code), p)
@@ -3458,7 +3731,10 @@ func (c *Client) StatusEdit(st Status) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3474,7 +3750,10 @@ func (c *Client) Stores() (StoresResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3488,7 +3767,7 @@ func (c *Client) StoreEdit(store Store) (SuccessfulResponse, int, error) {
 	objJSON, _ := json.Marshal(&store)
 
 	p := url.Values{
-		"store": {string(objJSON[:])},
+		"store": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/stores/%s/edit", store.Code), p)
@@ -3496,7 +3775,10 @@ func (c *Client) StoreEdit(store Store) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3512,7 +3794,10 @@ func (c *Client) Units() (UnitsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3526,7 +3811,7 @@ func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, error) {
 	objJSON, _ := json.Marshal(&unit)
 
 	p := url.Values{
-		"unit": {string(objJSON[:])},
+		"unit": {string(objJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/reference/units/%s/edit", unit.Code), p)
@@ -3534,7 +3819,10 @@ func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3545,10 +3833,10 @@ func (c *Client) UnitEdit(unit Unit) (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.Segments(SegmentsRequest{
-//		Filter: v5.SegmentsFilter{
+//		Filter: retailcrm.SegmentsFilter{
 //			Ids: []int{1,2,3}
 //		}
 //	})
@@ -3574,7 +3862,10 @@ func (c *Client) Segments(parameters SegmentsRequest) (SegmentsResponse, int, er
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3585,7 +3876,7 @@ func (c *Client) Segments(parameters SegmentsRequest) (SegmentsResponse, int, er
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.Settings()
 //
@@ -3606,7 +3897,10 @@ func (c *Client) Settings() (SettingsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3617,20 +3911,20 @@ func (c *Client) Settings() (SettingsResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Inventories(v5.InventoriesRequest{Filter: v5.InventoriesFilter{Details: 1, ProductActive: 1}, Page: 1})
+// 	data, status, err := client.Inventories(retailcrm.InventoriesRequest{Filter: retailcrm.InventoriesFilter{Details: 1, ProductActive: 1}, Page: 1})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Offers {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse, int, error) {
 	var resp InventoriesResponse
@@ -3642,7 +3936,10 @@ func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3653,10 +3950,10 @@ func (c *Client) Inventories(parameters InventoriesRequest) (InventoriesResponse
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.InventoriesUpload(
-//	   []v5.InventoryUpload{
+//	   []retailcrm.InventoryUpload{
 //		   {
 //			   XMLID: "pT22K9YzX21HTdzFCe1",
 //			   Stores: []InventoryUploadStore{
@@ -3691,7 +3988,7 @@ func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string
 	uploadJSON, _ := json.Marshal(&inventories)
 
 	p := url.Values{
-		"offers": {string(uploadJSON[:])},
+		"offers": {string(uploadJSON)},
 	}
 
 	fillSite(&p, site)
@@ -3701,7 +3998,10 @@ func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3712,9 +4012,9 @@ func (c *Client) InventoriesUpload(inventories []InventoryUpload, site ...string
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.PricesUpload([]v5.OfferPriceUpload{
+//	data, status, err := client.PricesUpload([]retailcrm.OfferPriceUpload{
 //		{
 //			ID         1
 //			Site       "store-1"
@@ -3742,7 +4042,7 @@ func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, i
 	uploadJSON, _ := json.Marshal(&prices)
 
 	p := url.Values{
-		"prices": {string(uploadJSON[:])},
+		"prices": {string(uploadJSON)},
 	}
 
 	data, status, err := c.PostRequest("/store/prices/upload", p)
@@ -3750,7 +4050,10 @@ func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, i
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3761,24 +4064,24 @@ func (c *Client) PricesUpload(prices []OfferPriceUpload) (StoreUploadResponse, i
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.ProductsGroup(v5.ProductsGroupsRequest{
-//		Filter: v5.ProductsGroupsFilter{
+// 	data, status, err := client.ProductsGroup(retailcrm.ProductsGroupsRequest{
+//		Filter: retailcrm.ProductsGroupsFilter{
 //			Active: 1,
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.ProductGroup {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroupsResponse, int, error) {
 	var resp ProductsGroupsResponse
@@ -3790,7 +4093,10 @@ func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroups
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3801,25 +4107,25 @@ func (c *Client) ProductsGroup(parameters ProductsGroupsRequest) (ProductsGroups
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Products(v5.ProductsRequest{
-//		Filter: v5.ProductsFilter{
+// 	data, status, err := client.Products(retailcrm.ProductsRequest{
+//		Filter: retailcrm.ProductsFilter{
 //			Active:   1,
 //			MinPrice: 1000,
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Products {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, error) {
 	var resp ProductsResponse
@@ -3831,7 +4137,10 @@ func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, er
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3842,24 +4151,24 @@ func (c *Client) Products(parameters ProductsRequest) (ProductsResponse, int, er
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.ProductsProperties(v5.ProductsPropertiesRequest{
-//		Filter: v5.ProductsPropertiesFilter{
+// 	data, status, err := client.ProductsProperties(retailcrm.ProductsPropertiesRequest{
+//		Filter: retailcrm.ProductsPropertiesFilter{
 //			Sites: []string["store"],
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Properties {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (ProductsPropertiesResponse, int, error) {
 	var resp ProductsPropertiesResponse
@@ -3871,7 +4180,10 @@ func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (Produ
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3882,24 +4194,24 @@ func (c *Client) ProductsProperties(parameters ProductsPropertiesRequest) (Produ
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Tasks(v5.TasksRequest{
+// 	data, status, err := client.Tasks(retailcrm.TasksRequest{
 //		Filter: TasksFilter{
 //			DateFrom: "2012-12-12",
 //		},
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Tasks {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, error) {
 	var resp TasksResponse
@@ -3911,7 +4223,10 @@ func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3922,30 +4237,30 @@ func (c *Client) Tasks(parameters TasksRequest) (TasksResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Tasks(v5.Task{
+// 	data, status, err := client.Tasks(retailcrm.Task{
 //		Text:        "task №1",
 //		PerformerID: 12,
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.ID)
+// 		log.Printf("%v\n", data.ID)
 // 	}
 func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
 	taskJSON, _ := json.Marshal(&task)
 
 	p := url.Values{
-		"task": {string(taskJSON[:])},
+		"task": {string(taskJSON)},
 	}
 
 	fillSite(&p, site)
@@ -3955,7 +4270,10 @@ func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, err
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -3966,20 +4284,20 @@ func (c *Client) TaskCreate(task Task, site ...string) (CreateResponse, int, err
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.Task(12)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.Task)
+// 		log.Printf("%v\n", data.Task)
 // 	}
 func (c *Client) Task(id int) (TaskResponse, int, error) {
 	var resp TaskResponse
@@ -3989,7 +4307,10 @@ func (c *Client) Task(id int) (TaskResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4000,19 +4321,19 @@ func (c *Client) Task(id int) (TaskResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Task(v5.Task{
+// 	data, status, err := client.Task(retailcrm.Task{
 //		ID:   12
 //		Text: "task №2",
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -4021,7 +4342,7 @@ func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, e
 	taskJSON, _ := json.Marshal(&task)
 
 	p := url.Values{
-		"task": {string(taskJSON[:])},
+		"task": {string(taskJSON)},
 	}
 
 	fillSite(&p, site)
@@ -4031,10 +4352,13 @@ func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, e
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
-	if resp.Success == false {
-		a := NewAPIError(data)
+	if !resp.Success {
+		a := CreateAPIError(data)
 		return resp, status, a
 	}
 
@@ -4047,20 +4371,20 @@ func (c *Client) TaskEdit(task Task, site ...string) (SuccessfulResponse, int, e
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.UserGroups(v5.UserGroupsRequest{Page: 1})
+// 	data, status, err := client.UserGroups(retailcrm.UserGroupsRequest{Page: 1})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Groups {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, int, error) {
 	var resp UserGroupsResponse
@@ -4072,7 +4396,10 @@ func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, i
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4083,20 +4410,20 @@ func (c *Client) UserGroups(parameters UserGroupsRequest) (UserGroupsResponse, i
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-// 	data, status, err := client.Users(v5.UsersRequest{Filter: v5.UsersFilter{Active: 1}, Page: 1})
+// 	data, status, err := client.Users(retailcrm.UsersRequest{Filter: retailcrm.UsersFilter{Active: 1}, Page: 1})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	for _, value := range data.Users {
-// 		fmt.Printf("%v\n", value)
+// 		log.Printf("%v\n", value)
 // 	}
 func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, error) {
 	var resp UsersResponse
@@ -4108,7 +4435,10 @@ func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4119,20 +4449,20 @@ func (c *Client) Users(parameters UsersRequest) (UsersResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.User(12)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.User)
+// 		log.Printf("%v\n", data.User)
 // 	}
 func (c *Client) User(id int) (UserResponse, int, error) {
 	var resp UserResponse
@@ -4142,7 +4472,10 @@ func (c *Client) User(id int) (UserResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4153,22 +4486,22 @@ func (c *Client) User(id int) (UserResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.UserStatus(12, "busy")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) UserStatus(id int, status string) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
 
 	p := url.Values{
-		"status": {string(status)},
+		"status": {status},
 	}
 
 	data, st, err := c.PostRequest(fmt.Sprintf("/users/%d/status", id), p)
@@ -4176,10 +4509,13 @@ func (c *Client) UserStatus(id int, status string) (SuccessfulResponse, int, err
 		return resp, st, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, st, err
+	}
 
-	if resp.Success == false {
-		return resp, st, NewAPIError(data)
+	if !resp.Success {
+		return resp, st, CreateAPIError(data)
 	}
 
 	return resp, st, nil
@@ -4196,7 +4532,10 @@ func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4207,7 +4546,7 @@ func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.Costs(CostsRequest{
 //		Filter: CostsFilter{
@@ -4217,15 +4556,15 @@ func (c *Client) StaticticsUpdate() (SuccessfulResponse, int, error) {
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.Costs {
-// 		fmt.Printf("%v\n", value.Summ)
+// 		log.Printf("%v\n", value.Summ)
 // 	}
 func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, error) {
 	var resp CostsResponse
@@ -4238,21 +4577,24 @@ func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
 
-// CostCreate create an cost
+// CostCreate create the cost
 //
 // For more information see http://www.retailcrm.pro/docs/Developers/ApiVersion5#post--api-v5-costs-create
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CostCreate(
-// 		v5.CostRecord{
+// 		retailcrm.CostRecord{
 //			DateFrom:  "2012-12-12",
 //			DateTo:    "2012-12-12",
 //			Summ:      12,
@@ -4266,15 +4608,15 @@ func (c *Client) Costs(costs CostsRequest) (CostsResponse, int, error) {
 // 	)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.ID)
+// 		log.Printf("%v", data.ID)
 // 	}
 func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -4282,7 +4624,7 @@ func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, in
 	costJSON, _ := json.Marshal(&cost)
 
 	p := url.Values{
-		"cost": {string(costJSON[:])},
+		"cost": {string(costJSON)},
 	}
 
 	fillSite(&p, site)
@@ -4292,7 +4634,10 @@ func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, in
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4303,20 +4648,20 @@ func (c *Client) CostCreate(cost CostRecord, site ...string) (CreateResponse, in
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.client.CostsDelete([]int{1, 2, 3, 48, 49, 50})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("Not removed costs: %v", data.NotRemovedIds)
+// 		log.Printf("Not removed costs: %v", data.NotRemovedIds)
 // 	}
 func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, error) {
 	var resp CostsDeleteResponse
@@ -4324,7 +4669,7 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, error) {
 	costJSON, _ := json.Marshal(&ids)
 
 	p := url.Values{
-		"ids": {string(costJSON[:])},
+		"ids": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest("/costs/delete", p)
@@ -4332,7 +4677,10 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4343,9 +4691,9 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.CostCreate([]v5.CostRecord{
+//	data, status, err := client.CostCreate([]retailcrm.CostRecord{
 //		{
 //			DateFrom:  "2012-12-12",
 //			DateTo:    "2012-12-12",
@@ -4365,15 +4713,15 @@ func (c *Client) CostsDelete(ids []int) (CostsDeleteResponse, int, error) {
 // 	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("Uploaded costs: %v", data.UploadedCosts)
+// 		log.Printf("Uploaded costs: %v", data.UploadedCosts)
 // 	}
 func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, error) {
 	var resp CostsUploadResponse
@@ -4381,7 +4729,7 @@ func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, error
 	costJSON, _ := json.Marshal(&cost)
 
 	p := url.Values{
-		"costs": {string(costJSON[:])},
+		"costs": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest("/costs/upload", p)
@@ -4389,7 +4737,10 @@ func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, error
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4400,20 +4751,20 @@ func (c *Client) CostsUpload(cost []CostRecord) (CostsUploadResponse, int, error
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.Cost(1)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.Cost)
+// 		log.Printf("%v", data.Cost)
 // 	}
 func (c *Client) Cost(id int) (CostResponse, int, error) {
 	var resp CostResponse
@@ -4424,7 +4775,10 @@ func (c *Client) Cost(id int) (CostResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4435,16 +4789,16 @@ func (c *Client) Cost(id int) (CostResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CostDelete(1)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) CostDelete(id int) (SuccessfulResponse, int, error) {
 	var resp SuccessfulResponse
@@ -4452,7 +4806,7 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, error) {
 	costJSON, _ := json.Marshal(&id)
 
 	p := url.Values{
-		"costs": {string(costJSON[:])},
+		"costs": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/costs/%d/delete", id), p)
@@ -4461,7 +4815,10 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4472,9 +4829,9 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.CostEdit(1, v5.Cost{
+//	data, status, err := client.CostEdit(1, retailcrm.Cost{
 //		DateFrom:  "2012-12-12",
 //		DateTo:    "2018-12-13",
 //		Summ:      321,
@@ -4482,15 +4839,15 @@ func (c *Client) CostDelete(id int) (SuccessfulResponse, int, error) {
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.Id)
+// 		log.Printf("%v", data.ID)
 // 	}
 func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateResponse, int, error) {
 	var resp CreateResponse
@@ -4498,7 +4855,7 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 	costJSON, _ := json.Marshal(&cost)
 
 	p := url.Values{
-		"cost": {string(costJSON[:])},
+		"cost": {string(costJSON)},
 	}
 
 	fillSite(&p, site)
@@ -4508,7 +4865,10 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4519,7 +4879,7 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.Files(FilesRequest{
 //		Filter: FilesFilter{
@@ -4528,11 +4888,11 @@ func (c *Client) CostEdit(id int, cost CostRecord, site ...string) (CreateRespon
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 func (c *Client) Files(files FilesRequest) (FilesResponse, int, error) {
 	var resp FilesResponse
@@ -4545,7 +4905,10 @@ func (c *Client) Files(files FilesRequest) (FilesResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4556,7 +4919,7 @@ func (c *Client) Files(files FilesRequest) (FilesResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //  file, err := os.Open("file.jpg")
 //  if err != nil {
@@ -4581,7 +4944,10 @@ func (c *Client) FileUpload(reader io.Reader) (FileUploadResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4592,20 +4958,20 @@ func (c *Client) FileUpload(reader io.Reader) (FileUploadResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 // 	data, status, err := client.File(112)
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 //	if data.Success == true {
-// 		fmt.Printf("%v\n", data.File)
+// 		log.Printf("%v\n", data.File)
 // 	}
 func (c *Client) File(id int) (FileResponse, int, error) {
 	var resp FileResponse
@@ -4615,7 +4981,10 @@ func (c *Client) File(id int) (FileResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4626,7 +4995,7 @@ func (c *Client) File(id int) (FileResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //  data, status, err := client.FileDelete(123)
 //
@@ -4646,7 +5015,10 @@ func (c *Client) FileDelete(id int) (SuccessfulResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4657,7 +5029,7 @@ func (c *Client) FileDelete(id int) (SuccessfulResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //  fileData, status, err := client.FileDownload(123)
 //
@@ -4684,7 +5056,7 @@ func (c *Client) FileDownload(id int) (io.ReadCloser, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //  data, status, err := client.FileEdit(123, File{Filename: "image2.jpg"})
 //
@@ -4709,7 +5081,10 @@ func (c *Client) FileEdit(id int, file File) (FileResponse, int, error) {
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4720,19 +5095,19 @@ func (c *Client) FileEdit(id int, file File) (FileResponse, int, error) {
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.CustomFields(v5.CustomFieldsRequest{
+//	data, status, err := client.CustomFields(retailcrm.CustomFieldsRequest{
 //		Type: "string",
 // 		Entity: "customer",
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	for _, value := range data.CustomFields {
@@ -4749,7 +5124,10 @@ func (c *Client) CustomFields(customFields CustomFieldsRequest) (CustomFieldsRes
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4760,10 +5138,10 @@ func (c *Client) CustomFields(customFields CustomFieldsRequest) (CustomFieldsRes
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.CustomDictionaries(v5.CustomDictionariesRequest{
-//		Filter: v5.CustomDictionariesFilter{
+//	data, status, err := client.CustomDictionaries(retailcrm.CustomDictionariesRequest{
+//		Filter: retailcrm.CustomDictionariesFilter{
 //			Name: "Dictionary-1",
 //		},
 //	})
@@ -4792,7 +5170,10 @@ func (c *Client) CustomDictionaries(customDictionaries CustomDictionariesRequest
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4803,9 +5184,9 @@ func (c *Client) CustomDictionaries(customDictionaries CustomDictionariesRequest
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.CustomDictionariesCreate(v5.CustomDictionary{
+//	data, status, err := client.CustomDictionariesCreate(retailcrm.CustomDictionary{
 //		Name: "Courier profiles",
 //		Code: "courier-profiles",
 //		Elements: []Element{
@@ -4837,7 +5218,7 @@ func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (Cu
 	costJSON, _ := json.Marshal(&customDictionary)
 
 	p := url.Values{
-		"customDictionary": {string(costJSON[:])},
+		"customDictionary": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest("/custom-fields/dictionaries/create", p)
@@ -4846,7 +5227,10 @@ func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (Cu
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4857,20 +5241,20 @@ func (c *Client) CustomDictionariesCreate(customDictionary CustomDictionary) (Cu
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CustomDictionary("courier-profiles")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.CustomDictionary.Name)
+// 		log.Printf("%v", data.CustomDictionary.Name)
 // 	}
 func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, error) {
 	var resp CustomDictionaryResponse
@@ -4881,7 +5265,10 @@ func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, e
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4892,9 +5279,9 @@ func (c *Client) CustomDictionary(code string) (CustomDictionaryResponse, int, e
 //
 // Example:
 //
-//	var client = v5.New("https://demo.url", "09jIJ")
+//	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
-//	data, status, err := client.CustomDictionaryEdit(v5.CustomDictionary{
+//	data, status, err := client.CustomDictionaryEdit(retailcrm.CustomDictionary{
 //	Name: "Courier profiles",
 //		Code: "courier-profiles",
 //		Elements: []Element{
@@ -4926,7 +5313,7 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 	costJSON, _ := json.Marshal(&customDictionary)
 
 	p := url.Values{
-		"customDictionary": {string(costJSON[:])},
+		"customDictionary": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/custom-fields/dictionaries/%s/edit", customDictionary.Code), p)
@@ -4934,7 +5321,10 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4945,7 +5335,7 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CustomFieldsCreate(CustomFields{
 //		Name:        "First order",
@@ -4956,15 +5346,15 @@ func (c *Client) CustomDictionaryEdit(customDictionary CustomDictionary) (Custom
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.Code)
+// 		log.Printf("%v", data.Code)
 // 	}
 func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse, int, error) {
 	var resp CustomResponse
@@ -4972,7 +5362,7 @@ func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse,
 	costJSON, _ := json.Marshal(&customFields)
 
 	p := url.Values{
-		"customField": {string(costJSON[:])},
+		"customField": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest(fmt.Sprintf("/custom-fields/%s/create", customFields.Entity), p)
@@ -4981,7 +5371,10 @@ func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse,
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -4992,20 +5385,20 @@ func (c *Client) CustomFieldsCreate(customFields CustomFields) (CustomResponse,
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CustomField("order", "first-order")
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.CustomField)
+// 		log.Printf("%v", data.CustomField)
 // 	}
 func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, error) {
 	var resp CustomFieldResponse
@@ -5016,7 +5409,10 @@ func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, err
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
@@ -5027,7 +5423,7 @@ func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, err
 //
 // Example:
 //
-// 	var client = v5.New("https://demo.url", "09jIJ")
+// 	var client = retailcrm.New("https://demo.url", "09jIJ")
 //
 //	data, status, err := client.CustomFieldEdit(CustomFields{
 //		Code:        "first-order",
@@ -5036,15 +5432,15 @@ func (c *Client) CustomField(entity, code string) (CustomFieldResponse, int, err
 //	})
 //
 // 	if err != nil {
-// 		fmt.Printf("%v", err.Error())
-// 	}
+// 		if apiErr, ok := retailcrm.AsAPIError(err); ok {
+// 			log.Fatalf("http status: %d, %s", status, apiErr.String())
+// 		}
 //
-// 	if status >= http.StatusBadRequest {
-// 		fmt.Printf("%v", err.ApiError())
+// 		log.Fatalf("http status: %d, error: %s", status, err)
 // 	}
 //
 // 	If data.Success == true {
-// 		fmt.Printf("%v", data.Code)
+// 		log.Printf("%v", data.Code)
 // 	}
 func (c *Client) CustomFieldEdit(customFields CustomFields) (CustomResponse, int, error) {
 	var resp CustomResponse
@@ -5052,7 +5448,7 @@ func (c *Client) CustomFieldEdit(customFields CustomFields) (CustomResponse, int
 	costJSON, _ := json.Marshal(&customFields)
 
 	p := url.Values{
-		"customField": {string(costJSON[:])},
+		"customField": {string(costJSON)},
 	}
 
 	data, status, err := c.PostRequest(
@@ -5063,7 +5459,10 @@ func (c *Client) CustomFieldEdit(customFields CustomFields) (CustomResponse, int
 		return resp, status, err
 	}
 
-	json.Unmarshal(data, &resp)
+	err = json.Unmarshal(data, &resp)
+	if err != nil {
+		return resp, status, err
+	}
 
 	return resp, status, nil
 }
diff --git a/v5/client_test.go b/client_test.go
similarity index 98%
rename from v5/client_test.go
rename to client_test.go
index c8687d7..3f102a2 100644
--- a/v5/client_test.go
+++ b/client_test.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 import (
 	"encoding/json"
@@ -20,14 +20,12 @@ import (
 )
 
 func TestMain(m *testing.M) {
-	if os.Getenv("DEVELOPER_NODE") == "1" {
-		err := godotenv.Load("../.env")
-		if err != nil {
-			log.Fatal("Error loading .env file")
-		}
-
-		os.Exit(m.Run())
+	err := godotenv.Load(".env")
+	if err != nil {
+		log.Fatal("Error loading .env file")
 	}
+
+	os.Exit(m.Run())
 }
 
 func init() {
@@ -494,7 +492,7 @@ func TestClient_CustomersUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Customers are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Customers are loaded with ErrorsList"}`)
 
 	data, _, err := c.CustomersUpload(customers)
 	if err == nil {
@@ -631,7 +629,7 @@ func TestClient_CustomersFixExternalIds_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"id": "ID must be an integer"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"id": "ID must be an integer"}}`)
 
 	data, _, err := c.CustomersFixExternalIds(customers)
 	if err == nil {
@@ -690,7 +688,7 @@ func TestClient_CustomersHistory_Fail(t *testing.T) {
 		Get("/customers/history").
 		MatchParam("filter[startDate]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[startDate]": "Значение недопустимо."}}`)
 
 	data, _, err := c.CustomersHistory(f)
 	if err == nil {
@@ -885,7 +883,7 @@ func TestClient_CorporateCustomersFixExternalIds_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"id": "ID must be an integer"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"id": "ID must be an integer"}}`)
 
 	data, _, err := c.CorporateCustomersFixExternalIds(customers)
 	if err == nil {
@@ -944,7 +942,7 @@ func TestClient_CorporateCustomersHistory_Fail(t *testing.T) {
 		Get("/customers-corporate/history").
 		MatchParam("filter[startDate]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[startDate]": "Значение недопустимо."}}`)
 
 	data, _, err := c.CorporateCustomersHistory(f)
 	if err == nil {
@@ -1130,7 +1128,7 @@ func TestClient_CorporateCustomersUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Customers are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Customers are loaded with ErrorsList"}`)
 
 	data, _, err := c.CorporateCustomersUpload(customers)
 	if err == nil {
@@ -1703,7 +1701,7 @@ func TestClient_NotesNotes_Fail(t *testing.T) {
 		Get("/customers/notes").
 		MatchParam("filter[createdAtFrom]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[createdAtFrom]": "This value is not valid."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[createdAtFrom]": "This value is not valid."}}`)
 
 	data, _, err := c.CustomerNotes(NotesRequest{
 		Filter: NotesFilter{CreatedAtFrom: "2020-13-12"},
@@ -1803,7 +1801,7 @@ func TestClient_NotesCreateDelete_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"customer": "Set one of the following fields: id, externalId"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "ErrorsList": {"customer": "Set one of the following fields: id, externalId"}}`)
 
 	data, _, err := c.CustomerNoteCreate(note)
 	if err == nil {
@@ -1875,7 +1873,7 @@ func TestClient_OrdersOrders_Fail(t *testing.T) {
 		Get("/orders").
 		MatchParam("filter[attachments]", "7").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[attachments]": "SThis value is not valid."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[attachments]": "SThis value is not valid."}}`)
 
 	data, _, err := c.Orders(OrdersRequest{Filter: OrdersFilter{Attachments: 7}})
 	if err == nil {
@@ -2166,7 +2164,7 @@ func TestClient_OrdersUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Orders are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Orders are loaded with ErrorsList"}`)
 
 	data, _, err := c.OrdersUpload(orders)
 	if err == nil {
@@ -2395,7 +2393,7 @@ func TestClient_OrdersHistory_Fail(t *testing.T) {
 		Get("/orders/history").
 		MatchParam("filter[startDate]", "2020-13-12").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"children[startDate]": "Значение недопустимо."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"children[startDate]": "Значение недопустимо."}}`)
 
 	data, _, err := c.OrdersHistory(OrdersHistoryRequest{Filter: OrdersHistoryFilter{StartDate: "2020-13-12"}})
 	if err == nil {
@@ -2521,7 +2519,7 @@ func TestClient_PaymentCreateEditDelete_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"order": "Set one of the following fields: id, externalId, number"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "ErrorsList": {"order": "Set one of the following fields: id, externalId, number"}}`)
 
 	data, _, err := c.OrderPaymentCreate(f)
 	if err == nil {
@@ -2743,7 +2741,7 @@ func TestClient_TaskChange_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Task is not loaded", "errors": {"performerId": "This value should not be blank."}}`)
+		BodyString(`{"success": false, "errorMsg": "Task is not loaded", "ErrorsList": {"performerId": "This value should not be blank."}}`)
 
 	data, _, err := c.TaskEdit(f)
 	if err == nil {
@@ -2792,7 +2790,7 @@ func TestClient_UsersUsers_Fail(t *testing.T) {
 		MatchParam("filter[active]", "3").
 		MatchParam("page", "1").
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "errors": {"active": "he value you selected is not a valid choice."}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the input parameters", "ErrorsList": {"active": "he value you selected is not a valid choice."}}`)
 
 	data, _, err := c.Users(UsersRequest{Filter: UsersFilter{Active: 3}, Page: 1})
 	if err == nil {
@@ -3550,8 +3548,8 @@ func TestClient_Courier(t *testing.T) {
 	cur := Courier{
 		Active:    true,
 		Email:     fmt.Sprintf("%s@example.com", RandomString(5)),
-		FirstName: fmt.Sprintf("%s", RandomString(5)),
-		LastName:  fmt.Sprintf("%s", RandomString(5)),
+		FirstName: RandomString(5),
+		LastName:  RandomString(5),
 	}
 
 	defer gock.Off()
@@ -3583,7 +3581,7 @@ func TestClient_Courier(t *testing.T) {
 	}
 
 	cur.ID = data.ID
-	cur.Patronymic = fmt.Sprintf("%s", RandomString(5))
+	cur.Patronymic = RandomString(5)
 
 	jr, _ = json.Marshal(&cur)
 
@@ -3629,7 +3627,7 @@ func TestClient_Courier_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(400).
-		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "errors": {"firstName": "Specify the first name"}}`)
+		BodyString(`{"success": false, "errorMsg": "Errors in the entity format", "ErrorsList": {"firstName": "Specify the first name"}}`)
 
 	data, st, err := c.CourierCreate(Courier{})
 	if err == nil {
@@ -3644,7 +3642,7 @@ func TestClient_Courier_Fail(t *testing.T) {
 		t.Error(successFail)
 	}
 
-	cur := Courier{Patronymic: fmt.Sprintf("%s", RandomString(5))}
+	cur := Courier{Patronymic: RandomString(5)}
 	jr, _ = json.Marshal(&cur)
 
 	p = url.Values{
@@ -5793,7 +5791,7 @@ func TestClient_CostsUpload_Fail(t *testing.T) {
 		MatchType("url").
 		BodyString(p.Encode()).
 		Reply(460).
-		BodyString(`{"success": false, "errorMsg": "Costs are loaded with errors"}`)
+		BodyString(`{"success": false, "errorMsg": "Costs are loaded with ErrorsList"}`)
 
 	data, _, err := c.CostsUpload(costsUpload)
 	if err == nil {
diff --git a/error.go b/error.go
new file mode 100644
index 0000000..01e946e
--- /dev/null
+++ b/error.go
@@ -0,0 +1,192 @@
+package retailcrm
+
+import (
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+var missingParameterMatcher = regexp.MustCompile(`^Parameter \'([\w\]\[\_\-]+)\' is missing$`)
+var (
+	// ErrMissingCredentials will be returned if no API key was provided to the API.
+	ErrMissingCredentials = NewAPIError(`apiKey is missing`)
+	// ErrInvalidCredentials will be returned if provided API key is invalid.
+	ErrInvalidCredentials = NewAPIError(`wrong "apiKey" value`)
+	// ErrAccessDenied will be returned in case of "Access denied" error.
+	ErrAccessDenied = NewAPIError("access denied")
+	// ErrAccountDoesNotExist will be returned if target system does not exist.
+	ErrAccountDoesNotExist = NewAPIError("account does not exist")
+	// ErrValidation will be returned in case of validation errors.
+	ErrValidation = NewAPIError("validation error")
+	// ErrMissingParameter will be returned if parameter is missing.
+	// Underlying error messages list will contain parameter name in the "Name" key.
+	ErrMissingParameter = NewAPIError("missing parameter")
+	// ErrGeneric will be returned if error cannot be classified as one of the errors above.
+	ErrGeneric = NewAPIError("API error")
+)
+
+// APIErrorsList struct.
+type APIErrorsList map[string]string
+
+// APIError returns when an API error was occurred.
+type APIError interface {
+	error
+	fmt.Stringer
+	withWrapped(error) APIError
+	withErrors(APIErrorsList) APIError
+	Unwrap() error
+	Errors() APIErrorsList
+}
+
+type apiError struct {
+	ErrorMsg   string        `json:"errorMsg,omitempty"`
+	ErrorsList APIErrorsList `json:"errors,omitempty"`
+	wrapped    error
+}
+
+// CreateAPIError from the provided response data. Different error types will be returned depending on the response,
+// all of them can be matched using errors.Is. APi errors will always implement APIError interface.
+func CreateAPIError(dataResponse []byte) error {
+	a := &apiError{}
+
+	if len(dataResponse) > 0 && dataResponse[0] == '<' {
+		return ErrAccountDoesNotExist
+	}
+
+	if err := json.Unmarshal(dataResponse, &a); err != nil {
+		return err
+	}
+
+	var found APIError
+	switch a.ErrorMsg {
+	case `"apiKey" is missing.`:
+		found = ErrMissingCredentials
+	case `Wrong "apiKey" value.`:
+		found = ErrInvalidCredentials
+	case "Access denied.":
+		found = ErrAccessDenied
+	case "Account does not exist.":
+		found = ErrAccountDoesNotExist
+	case "Errors in the entity format":
+		fallthrough
+	case "Validation error":
+		found = ErrValidation
+	default:
+		if param, ok := asMissingParameterErr(a.ErrorMsg); ok {
+			return a.withWrapped(ErrMissingParameter).withErrors(APIErrorsList{"Name": param})
+		}
+		found = ErrGeneric
+	}
+
+	result := NewAPIError(a.ErrorMsg).withWrapped(found)
+	if len(a.ErrorsList) > 0 {
+		return result.withErrors(a.ErrorsList)
+	}
+
+	return result
+}
+
+// CreateGenericAPIError for the situations when API response cannot be processed, but response was actually received.
+func CreateGenericAPIError(message string) APIError {
+	return NewAPIError(message).withWrapped(ErrGeneric)
+}
+
+// NewAPIError returns API error with the provided message.
+func NewAPIError(message string) APIError {
+	return &apiError{ErrorMsg: message}
+}
+
+// AsAPIError returns APIError and true if provided error is an APIError or contains wrapped APIError.
+// Returns (nil, false) otherwise.
+func AsAPIError(err error) (APIError, bool) {
+	apiErr := unwrapAPIError(err)
+	return apiErr, apiErr != nil
+}
+
+func unwrapAPIError(err error) APIError {
+	if err == nil {
+		return nil
+	}
+
+	if apiErr, ok := err.(APIError); ok { // nolint:errorlint
+		return apiErr
+	}
+
+	wrapper, ok := err.(interface { // nolint:errorlint
+		Unwrap() error
+	})
+	if ok {
+		return unwrapAPIError(wrapper.Unwrap())
+	}
+
+	return nil
+}
+
+// asMissingParameterErr returns true if "Parameter 'name' is missing" error message is provided.
+func asMissingParameterErr(message string) (string, bool) {
+	matches := missingParameterMatcher.FindAllStringSubmatch(message, -1)
+	if len(matches) == 1 && len(matches[0]) == 2 {
+		return matches[0][1], true
+	}
+	return "", false
+}
+
+// Error returns errorMsg field from the response.
+func (e *apiError) Error() string {
+	return e.ErrorMsg
+}
+
+// Unwrap returns wrapped error. It is usually one of the predefined types like ErrGeneric or ErrValidation.
+// It can be used directly, but it's main purpose is to make errors matchable via errors.Is call.
+func (e *apiError) Unwrap() error {
+	return e.wrapped
+}
+
+// Errors returns errors field from the response.
+func (e *apiError) Errors() APIErrorsList {
+	return e.ErrorsList
+}
+
+// String returns string representation of an APIError.
+func (e *apiError) String() string {
+	var sb strings.Builder
+	sb.Grow(256) // nolint:gomnd
+	sb.WriteString(fmt.Sprintf(`errorMsg: "%s"`, e.Error()))
+
+	if len(e.Errors()) > 0 {
+		i := 0
+		useIndex := true
+		errorList := make([]string, len(e.Errors()))
+
+		for index, errText := range e.Errors() {
+			if i == 0 && index == "0" {
+				useIndex = false
+			}
+
+			if useIndex {
+				errorList[i] = fmt.Sprintf(`%s: "%s"`, index, errText)
+			} else {
+				errorList[i] = errText
+			}
+
+			i++
+		}
+
+		sb.WriteString(", errors: [" + strings.Join(errorList, ", ") + "]")
+	}
+
+	return sb.String()
+}
+
+// withWrapped is a wrapped setter.
+func (e *apiError) withWrapped(err error) APIError {
+	e.wrapped = err
+	return e
+}
+
+// withErrors is an ErrorsList setter.
+func (e *apiError) withErrors(m APIErrorsList) APIError {
+	e.ErrorsList = m
+	return e
+}
diff --git a/error_test.go b/error_test.go
new file mode 100644
index 0000000..c860f27
--- /dev/null
+++ b/error_test.go
@@ -0,0 +1,171 @@
+package retailcrm
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+)
+
+type ErrorTest struct {
+	suite.Suite
+}
+
+func TestError(t *testing.T) {
+	suite.Run(t, new(ErrorTest))
+}
+
+func (t *ErrorTest) TestFailure_ApiErrorsSlice() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Failed to activate module",
+				"errors": [
+					"Your account has insufficient funds to activate integration module",
+					"Test error"
+				]}`)
+	expected := APIErrorsList{
+		"0": "Your account has insufficient funds to activate integration module",
+		"1": "Test error",
+	}
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().ErrorIs(e, ErrGeneric)
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().Equal(expected, apiErr.Errors())
+}
+
+func (t *ErrorTest) TestFailure_ApiErrorsMap() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Failed to activate module",
+				"errors": {"id": "ID must be an integer", "test": "Test error"}}`,
+	)
+	expected := APIErrorsList{
+		"id":   "ID must be an integer",
+		"test": "Test error",
+	}
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().ErrorIs(e, ErrGeneric)
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().Equal(expected, apiErr.Errors())
+}
+
+func (t *ErrorTest) TestFailure_APIKeyMissing() {
+	b := []byte(`{"success": false,
+				"errorMsg": "\"apiKey\" is missing."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrMissingCredentials)
+}
+
+func (t *ErrorTest) TestFailure_APIKeyWrong() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Wrong \"apiKey\" value."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrInvalidCredentials)
+}
+
+func (t *ErrorTest) TestFailure_AccessDenied() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Access denied."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrAccessDenied)
+}
+
+func (t *ErrorTest) TestFailure_AccountDoesNotExist() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Account does not exist."}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrAccountDoesNotExist)
+}
+
+func (t *ErrorTest) TestFailure_Validation() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Errors in the entity format",
+				"errors": {"name": "name must be provided"}}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrValidation)
+	t.Assert().Equal("name must be provided", apiErr.Errors()["name"])
+}
+
+func (t *ErrorTest) TestFailure_Validation2() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Validation error",
+				"errors": {"name": "name must be provided"}}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrValidation)
+	t.Assert().Equal("name must be provided", apiErr.Errors()["name"])
+	t.Assert().Equal("errorMsg: \"Validation error\", errors: [name: \"name must be provided\"]", apiErr.String())
+}
+
+func (t *ErrorTest) TestFailure_MissingParameter() {
+	b := []byte(`{"success": false,
+				"errorMsg": "Parameter 'item' is missing"}`,
+	)
+
+	e := CreateAPIError(b)
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Require().ErrorIs(e, ErrMissingParameter)
+	t.Assert().Equal("item", apiErr.Errors()["Name"])
+}
+
+func (t *ErrorTest) Test_CreateGenericAPIError() {
+	e := CreateGenericAPIError("generic error message")
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().ErrorIs(apiErr, ErrGeneric)
+	t.Assert().Equal("generic error message", e.Error())
+}
+
+func (t *ErrorTest) TestFailure_HTML() {
+	e := CreateAPIError([]byte{'<'})
+	apiErr, ok := AsAPIError(e)
+
+	t.Require().NotNil(apiErr)
+	t.Require().True(ok)
+	t.Assert().ErrorIs(apiErr, ErrAccountDoesNotExist)
+}
diff --git a/v5/filters.go b/filters.go
similarity index 99%
rename from v5/filters.go
rename to filters.go
index 1956ac8..b393f9f 100644
--- a/v5/filters.go
+++ b/filters.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 // CustomersFilter type.
 type CustomersFilter struct {
diff --git a/go.mod b/go.mod
index 5b744cd..2d1f311 100644
--- a/go.mod
+++ b/go.mod
@@ -1,12 +1,10 @@
-module github.com/retailcrm/api-client-go
+module github.com/retailcrm/api-client-go/v2
 
 go 1.13
 
 require (
 	github.com/google/go-querystring v1.1.0
 	github.com/joho/godotenv v1.3.0
-	golang.org/x/net v0.0.0-20191021144547-ec77196f6094 // indirect
-	golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543
-	gopkg.in/h2non/gentleman.v1 v1.0.4 // indirect
+	github.com/stretchr/testify v1.7.0
 	gopkg.in/h2non/gock.v1 v1.1.2
 )
diff --git a/go.sum b/go.sum
index 96ce52e..0fc530c 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/google/go-cmp v0.5.2 h1:X2ev0eStA3AbceY54o37/0PQ/UWqKEiiO2dKL5OPaFM=
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-querystring v1.1.0 h1:AnCroh3fv4ZBgVIf1Iwtovgjaw/GiKJo8M8yD/fhyJ8=
@@ -8,14 +10,16 @@ github.com/joho/godotenv v1.3.0 h1:Zjp+RcGpHhGlrMbJzXTrZZPrWj+1vfm90La1wgB6Bhc=
 github.com/joho/godotenv v1.3.0/go.mod h1:7hK45KPybAkOC6peb+G5yklZfMxEjkZhHbwpqxOKXbg=
 github.com/nbio/st v0.0.0-20140626010706-e9e8d9816f32 h1:W6apQkHrMkS0Muv8G/TipAy/FJl/rCYT0+EuS8+Z0z4=
 github.com/nbio/st v0.0.0-20140626010706-e9e8d9816f32/go.mod h1:9wM+0iRr9ahx58uYLpLIr5fm8diHn0JbqRycJi6w0Ms=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/net v0.0.0-20191021144547-ec77196f6094/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-gopkg.in/h2non/gentleman.v1 v1.0.4/go.mod h1:JYuHVdFzS4MKOXe0o+chKJ4hCe6tqKKw9XH9YP6WFrg=
-gopkg.in/h2non/gock.v1 v1.0.16 h1:F11k+OafeuFENsjei5t2vMTSTs9L62AdyTe4E1cgdG8=
-gopkg.in/h2non/gock.v1 v1.0.16/go.mod h1:XVuDAssexPLwgxCLMvDTWNU5eqklsydR6I5phZ9oPB8=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/h2non/gock.v1 v1.1.2 h1:jBbHXgGBK/AoPVfJh5x4r/WxIrElvbLel8TCZkkZJoY=
 gopkg.in/h2non/gock.v1 v1.1.2/go.mod h1:n7UGz/ckNChHiK05rDoiC4MYSunEC/lyaUm2WWaDva0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/log.go b/log.go
new file mode 100644
index 0000000..9ec3dff
--- /dev/null
+++ b/log.go
@@ -0,0 +1,25 @@
+package retailcrm
+
+// BasicLogger provides basic functionality for logging.
+type BasicLogger interface {
+	Printf(string, ...interface{})
+}
+
+// DebugLogger can be used to easily wrap any logger with Debugf method into the BasicLogger instance.
+type DebugLogger interface {
+	Debugf(string, ...interface{})
+}
+
+type debugLoggerAdapter struct {
+	logger DebugLogger
+}
+
+// DebugLoggerAdapter returns BasicLogger that calls underlying DebugLogger.Debugf.
+func DebugLoggerAdapter(logger DebugLogger) BasicLogger {
+	return &debugLoggerAdapter{logger: logger}
+}
+
+// Printf data in the log using DebugLogger.Debugf.
+func (l *debugLoggerAdapter) Printf(format string, v ...interface{}) {
+	l.logger.Debugf(format, v...)
+}
diff --git a/log_test.go b/log_test.go
new file mode 100644
index 0000000..8697dc9
--- /dev/null
+++ b/log_test.go
@@ -0,0 +1,24 @@
+package retailcrm
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type wrappedLogger struct {
+	lastMessage string
+}
+
+func (w *wrappedLogger) Debugf(msg string, v ...interface{}) {
+	w.lastMessage = fmt.Sprintf(msg, v...)
+}
+
+func TestDebugLoggerAdapter_Printf(t *testing.T) {
+	wrapped := &wrappedLogger{}
+	logger := DebugLoggerAdapter(wrapped)
+	logger.Printf("Test message #%d", 1)
+
+	assert.Equal(t, "Test message #1", wrapped.lastMessage)
+}
diff --git a/marshaling.go b/marshaling.go
new file mode 100644
index 0000000..06841e2
--- /dev/null
+++ b/marshaling.go
@@ -0,0 +1,102 @@
+package retailcrm
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+)
+
+func (t Tag) MarshalJSON() ([]byte, error) {
+	return json.Marshal(t.Name)
+}
+
+func (a *APIErrorsList) UnmarshalJSON(data []byte) error {
+	var i interface{}
+	var m APIErrorsList
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+
+	switch e := i.(type) {
+	case map[string]interface{}:
+		m = make(APIErrorsList, len(e))
+		for idx, val := range e {
+			m[idx] = fmt.Sprint(val)
+		}
+	case []interface{}:
+		m = make(APIErrorsList, len(e))
+		for idx, val := range e {
+			m[strconv.Itoa(idx)] = fmt.Sprint(val)
+		}
+	}
+
+	*a = m
+	return nil
+}
+
+func (l *CustomFieldsList) UnmarshalJSON(data []byte) error {
+	var i interface{}
+	var m CustomFieldsList
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+
+	switch e := i.(type) {
+	case map[string]interface{}:
+		m = make(CustomFieldsList, len(e))
+		for idx, val := range e {
+			m[idx] = fmt.Sprint(val)
+		}
+	case []interface{}:
+		m = make(CustomFieldsList, len(e))
+		for idx, val := range e {
+			m[strconv.Itoa(idx)] = fmt.Sprint(val)
+		}
+	}
+
+	*l = m
+	return nil
+}
+
+func (p *OrderPayments) UnmarshalJSON(data []byte) error {
+	var i interface{}
+	var m OrderPayments
+	if err := json.Unmarshal(data, &i); err != nil {
+		return err
+	}
+
+	switch e := i.(type) {
+	case map[string]interface{}:
+		m = make(OrderPayments, len(e))
+		for idx, val := range e {
+			var res OrderPayment
+			err := unmarshalMap(val.(map[string]interface{}), &res)
+			if err != nil {
+				return err
+			}
+			m[idx] = res
+		}
+	case []interface{}:
+		m = make(OrderPayments, len(e))
+		for idx, val := range e {
+			var res OrderPayment
+			err := unmarshalMap(val.(map[string]interface{}), &res)
+			if err != nil {
+				return err
+			}
+			m[strconv.Itoa(idx)] = res
+		}
+	}
+
+	*p = m
+	return nil
+}
+
+func unmarshalMap(m map[string]interface{}, v interface{}) (err error) {
+	var data []byte
+	data, err = json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(data, v)
+}
diff --git a/marshaling_test.go b/marshaling_test.go
new file mode 100644
index 0000000..256236e
--- /dev/null
+++ b/marshaling_test.go
@@ -0,0 +1,69 @@
+package retailcrm
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTag_MarshalJSON(t *testing.T) {
+	tags := []Tag{
+		{"first", "#3e89b6", false},
+		{"second", "#ffa654", false},
+	}
+	names := []byte(`["first","second"]`)
+	str, err := json.Marshal(tags)
+
+	if err != nil {
+		t.Errorf("%v", err.Error())
+	}
+
+	if !reflect.DeepEqual(str, names) {
+		t.Errorf("Marshaled: %#v\nExpected: %#v\n", str, names)
+	}
+}
+
+func TestAPIErrorsList_UnmarshalJSON(t *testing.T) {
+	var list APIErrorsList
+
+	require.NoError(t, json.Unmarshal([]byte(`["first", "second"]`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["0"], "first")
+	assert.Equal(t, list["1"], "second")
+
+	require.NoError(t, json.Unmarshal([]byte(`{"a": "first", "b": "second"}`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["a"], "first")
+	assert.Equal(t, list["b"], "second")
+}
+
+func TestCustomFieldsList_UnmarshalJSON(t *testing.T) {
+	var list CustomFieldsList
+
+	require.NoError(t, json.Unmarshal([]byte(`["first", "second"]`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["0"], "first")
+	assert.Equal(t, list["1"], "second")
+
+	require.NoError(t, json.Unmarshal([]byte(`{"a": "first", "b": "second"}`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["a"], "first")
+	assert.Equal(t, list["b"], "second")
+}
+
+func TestOrderPayments_UnmarshalJSON(t *testing.T) {
+	var list OrderPayments
+
+	require.NoError(t, json.Unmarshal([]byte(`[{"id": 1}, {"id": 2}]`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["0"], OrderPayment{ID: 1})
+	assert.Equal(t, list["1"], OrderPayment{ID: 2})
+
+	require.NoError(t, json.Unmarshal([]byte(`{"a": {"id": 1}, "b": {"id": 2}}`), &list))
+	assert.Len(t, list, 2)
+	assert.Equal(t, list["a"], OrderPayment{ID: 1})
+	assert.Equal(t, list["b"], OrderPayment{ID: 2})
+}
diff --git a/v5/request.go b/request.go
similarity index 97%
rename from v5/request.go
rename to request.go
index 8899845..d0616fe 100644
--- a/v5/request.go
+++ b/request.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 // CustomerRequest type.
 type CustomerRequest struct {
@@ -177,8 +177,8 @@ type ProductsPropertiesRequest struct {
 type DeliveryTrackingRequest struct {
 	DeliveryID  string                  `json:"deliveryId,omitempty"`
 	TrackNumber string                  `json:"trackNumber,omitempty"`
-	History     []DeliveryHistoryRecord `json:"history,omitempty,brackets"`
-	ExtraData   map[string]string       `json:"extraData,omitempty,brackets"`
+	History     []DeliveryHistoryRecord `json:"history,omitempty"`
+	ExtraData   map[string]string       `json:"extraData,omitempty"`
 }
 
 // DeliveryShipmentsRequest type.
diff --git a/v5/response.go b/response.go
similarity index 98%
rename from v5/response.go
rename to response.go
index 3dde1ea..5b753c9 100644
--- a/v5/response.go
+++ b/response.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 // SuccessfulResponse type.
 type SuccessfulResponse struct {
@@ -20,7 +20,7 @@ type OrderCreateResponse struct {
 // OperationResponse type.
 type OperationResponse struct {
 	Success bool              `json:"success"`
-	Errors  map[string]string `json:"errors,omitempty"`
+	Errors  map[string]string `json:"ErrorsList,omitempty"`
 }
 
 // VersionResponse return available API versions.
@@ -31,7 +31,7 @@ type VersionResponse struct {
 
 // CredentialResponse return available API methods.
 type CredentialResponse struct {
-	Success        bool     `json:"success,omitempty"`
+	Success bool `json:"success,omitempty"`
 	// deprecated
 	Credentials    []string `json:"credentials,omitempty"`
 	Scopes         []string `json:"scopes,omitempty"`
@@ -409,7 +409,7 @@ type ResponseInfo struct {
 
 // MgInfo type.
 type MgInfo struct {
-	EndpointUrl string `json:"endpointUrl"`
+	EndpointURL string `json:"endpointUrl"`
 	Token       string `json:"token"`
 }
 
diff --git a/v5/types.go b/types.go
similarity index 83%
rename from v5/types.go
rename to types.go
index bbeae59..ca9b2b4 100644
--- a/v5/types.go
+++ b/types.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 import (
 	"encoding/json"
@@ -19,6 +19,7 @@ type Client struct {
 	Key        string
 	Debug      bool
 	httpClient *http.Client
+	logger     BasicLogger
 }
 
 // Pagination type.
@@ -121,41 +122,41 @@ Customer related types
 
 // Customer type.
 type Customer struct {
-	ID                           int               `json:"id,omitempty"`
-	ExternalID                   string            `json:"externalId,omitempty"`
-	FirstName                    string            `json:"firstName,omitempty"`
-	LastName                     string            `json:"lastName,omitempty"`
-	Patronymic                   string            `json:"patronymic,omitempty"`
-	Sex                          string            `json:"sex,omitempty"`
-	Email                        string            `json:"email,omitempty"`
-	Phones                       []Phone           `json:"phones,omitempty"`
-	Address                      *Address          `json:"address,omitempty"`
-	CreatedAt                    string            `json:"createdAt,omitempty"`
-	Birthday                     string            `json:"birthday,omitempty"`
-	ManagerID                    int               `json:"managerId,omitempty"`
-	Vip                          bool              `json:"vip,omitempty"`
-	Bad                          bool              `json:"bad,omitempty"`
-	Site                         string            `json:"site,omitempty"`
-	Source                       *Source           `json:"source,omitempty"`
-	Contragent                   *Contragent       `json:"contragent,omitempty"`
-	PersonalDiscount             float32           `json:"personalDiscount,omitempty"`
-	CumulativeDiscount           float32           `json:"cumulativeDiscount,omitempty"`
-	DiscountCardNumber           string            `json:"discountCardNumber,omitempty"`
-	EmailMarketingUnsubscribedAt string            `json:"emailMarketingUnsubscribedAt,omitempty"`
-	AvgMarginSumm                float32           `json:"avgMarginSumm,omitempty"`
-	MarginSumm                   float32           `json:"marginSumm,omitempty"`
-	TotalSumm                    float32           `json:"totalSumm,omitempty"`
-	AverageSumm                  float32           `json:"averageSumm,omitempty"`
-	OrdersCount                  int               `json:"ordersCount,omitempty"`
-	CostSumm                     float32           `json:"costSumm,omitempty"`
-	MaturationTime               int               `json:"maturationTime,omitempty"`
-	FirstClientID                string            `json:"firstClientId,omitempty"`
-	LastClientID                 string            `json:"lastClientId,omitempty"`
-	BrowserID                    string            `json:"browserId,omitempty"`
-	MgCustomerID                 string            `json:"mgCustomerId,omitempty"`
-	PhotoURL                     string            `json:"photoUrl,omitempty"`
-	CustomFields                 map[string]string `json:"customFields,omitempty"`
-	Tags                         []Tag             `json:"tags,omitempty"`
+	ID                           int              `json:"id,omitempty"`
+	ExternalID                   string           `json:"externalId,omitempty"`
+	FirstName                    string           `json:"firstName,omitempty"`
+	LastName                     string           `json:"lastName,omitempty"`
+	Patronymic                   string           `json:"patronymic,omitempty"`
+	Sex                          string           `json:"sex,omitempty"`
+	Email                        string           `json:"email,omitempty"`
+	Phones                       []Phone          `json:"phones,omitempty"`
+	Address                      *Address         `json:"address,omitempty"`
+	CreatedAt                    string           `json:"createdAt,omitempty"`
+	Birthday                     string           `json:"birthday,omitempty"`
+	ManagerID                    int              `json:"managerId,omitempty"`
+	Vip                          bool             `json:"vip,omitempty"`
+	Bad                          bool             `json:"bad,omitempty"`
+	Site                         string           `json:"site,omitempty"`
+	Source                       *Source          `json:"source,omitempty"`
+	Contragent                   *Contragent      `json:"contragent,omitempty"`
+	PersonalDiscount             float32          `json:"personalDiscount,omitempty"`
+	CumulativeDiscount           float32          `json:"cumulativeDiscount,omitempty"`
+	DiscountCardNumber           string           `json:"discountCardNumber,omitempty"`
+	EmailMarketingUnsubscribedAt string           `json:"emailMarketingUnsubscribedAt,omitempty"`
+	AvgMarginSumm                float32          `json:"avgMarginSumm,omitempty"`
+	MarginSumm                   float32          `json:"marginSumm,omitempty"`
+	TotalSumm                    float32          `json:"totalSumm,omitempty"`
+	AverageSumm                  float32          `json:"averageSumm,omitempty"`
+	OrdersCount                  int              `json:"ordersCount,omitempty"`
+	CostSumm                     float32          `json:"costSumm,omitempty"`
+	MaturationTime               int              `json:"maturationTime,omitempty"`
+	FirstClientID                string           `json:"firstClientId,omitempty"`
+	LastClientID                 string           `json:"lastClientId,omitempty"`
+	BrowserID                    string           `json:"browserId,omitempty"`
+	MgCustomerID                 string           `json:"mgCustomerId,omitempty"`
+	PhotoURL                     string           `json:"photoUrl,omitempty"`
+	CustomFields                 CustomFieldsList `json:"customFields,omitempty"`
+	Tags                         []Tag            `json:"tags,omitempty"`
 }
 
 // CorporateCustomer type.
@@ -166,7 +167,7 @@ type CorporateCustomer struct {
 	CreatedAt          string                     `json:"createdAt,omitempty"`
 	Vip                bool                       `json:"vip,omitempty"`
 	Bad                bool                       `json:"bad,omitempty"`
-	CustomFields       map[string]string          `json:"customFields,omitempty"`
+	CustomFields       CustomFieldsList           `json:"customFields,omitempty"`
 	PersonalDiscount   float32                    `json:"personalDiscount,omitempty"`
 	DiscountCardNumber string                     `json:"discountCardNumber,omitempty"`
 	ManagerID          int                        `json:"managerId,omitempty"`
@@ -217,17 +218,17 @@ type CorporateCustomerContactCustomer struct {
 }
 
 type Company struct {
-	ID           int               `json:"id,omitempty"`
-	IsMain       bool              `json:"isMain,omitempty"`
-	ExternalID   string            `json:"externalId,omitempty"`
-	Active       bool              `json:"active,omitempty"`
-	Name         string            `json:"name,omitempty"`
-	Brand        string            `json:"brand,omitempty"`
-	Site         string            `json:"site,omitempty"`
-	CreatedAt    string            `json:"createdAt,omitempty"`
-	Contragent   *Contragent       `json:"contragent,omitempty"`
-	Address      *IdentifiersPair  `json:"address,omitempty"`
-	CustomFields map[string]string `json:"customFields,omitempty"`
+	ID           int              `json:"id,omitempty"`
+	IsMain       bool             `json:"isMain,omitempty"`
+	ExternalID   string           `json:"externalId,omitempty"`
+	Active       bool             `json:"active,omitempty"`
+	Name         string           `json:"name,omitempty"`
+	Brand        string           `json:"brand,omitempty"`
+	Site         string           `json:"site,omitempty"`
+	CreatedAt    string           `json:"createdAt,omitempty"`
+	Contragent   *Contragent      `json:"contragent,omitempty"`
+	Address      *IdentifiersPair `json:"address,omitempty"`
+	CustomFields CustomFieldsList `json:"customFields,omitempty"`
 }
 
 // CorporateCustomerNote type.
@@ -272,57 +273,60 @@ type CorporateCustomerHistoryRecord struct {
 Order related types
 */
 
+type OrderPayments map[string]OrderPayment
+type CustomFieldsList map[string]string
+
 // Order type.
 type Order struct {
-	ID                            int                     `json:"id,omitempty"`
-	ExternalID                    string                  `json:"externalId,omitempty"`
-	Number                        string                  `json:"number,omitempty"`
-	FirstName                     string                  `json:"firstName,omitempty"`
-	LastName                      string                  `json:"lastName,omitempty"`
-	Patronymic                    string                  `json:"patronymic,omitempty"`
-	Email                         string                  `json:"email,omitempty"`
-	Phone                         string                  `json:"phone,omitempty"`
-	AdditionalPhone               string                  `json:"additionalPhone,omitempty"`
-	CreatedAt                     string                  `json:"createdAt,omitempty"`
-	StatusUpdatedAt               string                  `json:"statusUpdatedAt,omitempty"`
-	ManagerID                     int                     `json:"managerId,omitempty"`
-	Mark                          int                     `json:"mark,omitempty"`
-	Call                          bool                    `json:"call,omitempty"`
-	Expired                       bool                    `json:"expired,omitempty"`
-	FromAPI                       bool                    `json:"fromApi,omitempty"`
-	MarkDatetime                  string                  `json:"markDatetime,omitempty"`
-	CustomerComment               string                  `json:"customerComment,omitempty"`
-	ManagerComment                string                  `json:"managerComment,omitempty"`
-	Status                        string                  `json:"status,omitempty"`
-	StatusComment                 string                  `json:"statusComment,omitempty"`
-	FullPaidAt                    string                  `json:"fullPaidAt,omitempty"`
-	Site                          string                  `json:"site,omitempty"`
-	OrderType                     string                  `json:"orderType,omitempty"`
-	OrderMethod                   string                  `json:"orderMethod,omitempty"`
-	CountryIso                    string                  `json:"countryIso,omitempty"`
-	Summ                          float32                 `json:"summ,omitempty"`
-	TotalSumm                     float32                 `json:"totalSumm,omitempty"`
-	PrepaySum                     float32                 `json:"prepaySum,omitempty"`
-	PurchaseSumm                  float32                 `json:"purchaseSumm,omitempty"`
-	DiscountManualAmount          float32                 `json:"discountManualAmount,omitempty"`
-	DiscountManualPercent         float32                 `json:"discountManualPercent,omitempty"`
-	Weight                        float32                 `json:"weight,omitempty"`
-	Length                        int                     `json:"length,omitempty"`
-	Width                         int                     `json:"width,omitempty"`
-	Height                        int                     `json:"height,omitempty"`
-	ShipmentStore                 string                  `json:"shipmentStore,omitempty"`
-	ShipmentDate                  string                  `json:"shipmentDate,omitempty"`
-	ClientID                      string                  `json:"clientId,omitempty"`
-	Shipped                       bool                    `json:"shipped,omitempty"`
-	UploadedToExternalStoreSystem bool                    `json:"uploadedToExternalStoreSystem,omitempty"`
-	Source                        *Source                 `json:"source,omitempty"`
-	Contragent                    *Contragent             `json:"contragent,omitempty"`
-	Customer                      *Customer               `json:"customer,omitempty"`
-	Delivery                      *OrderDelivery          `json:"delivery,omitempty"`
-	Marketplace                   *OrderMarketplace       `json:"marketplace,omitempty"`
-	Items                         []OrderItem             `json:"items,omitempty"`
-	CustomFields                  map[string]string       `json:"customFields,omitempty"`
-	Payments                      map[string]OrderPayment `json:"payments,omitempty"`
+	ID                            int               `json:"id,omitempty"`
+	ExternalID                    string            `json:"externalId,omitempty"`
+	Number                        string            `json:"number,omitempty"`
+	FirstName                     string            `json:"firstName,omitempty"`
+	LastName                      string            `json:"lastName,omitempty"`
+	Patronymic                    string            `json:"patronymic,omitempty"`
+	Email                         string            `json:"email,omitempty"`
+	Phone                         string            `json:"phone,omitempty"`
+	AdditionalPhone               string            `json:"additionalPhone,omitempty"`
+	CreatedAt                     string            `json:"createdAt,omitempty"`
+	StatusUpdatedAt               string            `json:"statusUpdatedAt,omitempty"`
+	ManagerID                     int               `json:"managerId,omitempty"`
+	Mark                          int               `json:"mark,omitempty"`
+	Call                          bool              `json:"call,omitempty"`
+	Expired                       bool              `json:"expired,omitempty"`
+	FromAPI                       bool              `json:"fromApi,omitempty"`
+	MarkDatetime                  string            `json:"markDatetime,omitempty"`
+	CustomerComment               string            `json:"customerComment,omitempty"`
+	ManagerComment                string            `json:"managerComment,omitempty"`
+	Status                        string            `json:"status,omitempty"`
+	StatusComment                 string            `json:"statusComment,omitempty"`
+	FullPaidAt                    string            `json:"fullPaidAt,omitempty"`
+	Site                          string            `json:"site,omitempty"`
+	OrderType                     string            `json:"orderType,omitempty"`
+	OrderMethod                   string            `json:"orderMethod,omitempty"`
+	CountryIso                    string            `json:"countryIso,omitempty"`
+	Summ                          float32           `json:"summ,omitempty"`
+	TotalSumm                     float32           `json:"totalSumm,omitempty"`
+	PrepaySum                     float32           `json:"prepaySum,omitempty"`
+	PurchaseSumm                  float32           `json:"purchaseSumm,omitempty"`
+	DiscountManualAmount          float32           `json:"discountManualAmount,omitempty"`
+	DiscountManualPercent         float32           `json:"discountManualPercent,omitempty"`
+	Weight                        float32           `json:"weight,omitempty"`
+	Length                        int               `json:"length,omitempty"`
+	Width                         int               `json:"width,omitempty"`
+	Height                        int               `json:"height,omitempty"`
+	ShipmentStore                 string            `json:"shipmentStore,omitempty"`
+	ShipmentDate                  string            `json:"shipmentDate,omitempty"`
+	ClientID                      string            `json:"clientId,omitempty"`
+	Shipped                       bool              `json:"shipped,omitempty"`
+	UploadedToExternalStoreSystem bool              `json:"uploadedToExternalStoreSystem,omitempty"`
+	Source                        *Source           `json:"source,omitempty"`
+	Contragent                    *Contragent       `json:"contragent,omitempty"`
+	Customer                      *Customer         `json:"customer,omitempty"`
+	Delivery                      *OrderDelivery    `json:"delivery,omitempty"`
+	Marketplace                   *OrderMarketplace `json:"marketplace,omitempty"`
+	Items                         []OrderItem       `json:"items,omitempty"`
+	CustomFields                  CustomFieldsList  `json:"customFields,omitempty"`
+	Payments                      OrderPayments     `json:"payments,omitempty"`
 }
 
 // OrdersStatus type.
@@ -378,8 +382,14 @@ type OrderDeliveryData struct {
 // UnmarshalJSON method.
 func (v *OrderDeliveryData) UnmarshalJSON(b []byte) error {
 	var additionalData map[string]interface{}
-	json.Unmarshal(b, &additionalData)
-	json.Unmarshal(b, &v.OrderDeliveryDataBasic)
+	err := json.Unmarshal(b, &additionalData)
+	if err != nil {
+		return err
+	}
+	err = json.Unmarshal(b, &v.OrderDeliveryDataBasic)
+	if err != nil {
+		return err
+	}
 	object := reflect.TypeOf(v.OrderDeliveryDataBasic)
 
 	for i := 0; i < object.NumField(); i++ {
@@ -401,7 +411,10 @@ func (v *OrderDeliveryData) UnmarshalJSON(b []byte) error {
 func (v OrderDeliveryData) MarshalJSON() ([]byte, error) {
 	result := map[string]interface{}{}
 	data, _ := json.Marshal(v.OrderDeliveryDataBasic)
-	json.Unmarshal(data, &result)
+	err := json.Unmarshal(data, &result)
+	if err != nil {
+		return nil, err
+	}
 
 	for key, value := range v.AdditionalFields {
 		result[key] = value
@@ -587,7 +600,7 @@ type User struct {
 	Phone      string      `json:"phone,omitempty"`
 	Status     string      `json:"status,omitempty"`
 	Groups     []UserGroup `json:"groups,omitempty"`
-	MgUserId   uint64      `json:"mgUserId,omitempty"`
+	MGUserID   uint64      `json:"mgUserId,omitempty"`
 }
 
 // UserGroup type.
@@ -1054,7 +1067,7 @@ type Action struct {
 
 // MgTransport type.
 type MgTransport struct {
-	WebhookUrl string `json:"webhookUrl,omitempty"`
+	WebhookURL string `json:"webhookUrl,omitempty"`
 }
 
 // MgBot type.
@@ -1072,7 +1085,7 @@ type CostRecord struct {
 	DateTo   string   `json:"dateTo,omitempty"`
 	Summ     float32  `json:"summ,omitempty"`
 	CostItem string   `json:"costItem,omitempty"`
-	UserId   int      `json:"userId,omitempty"`
+	UserID   int      `json:"userId,omitempty"`
 	Order    *Order   `json:"order,omitempty"`
 	Sites    []string `json:"sites,omitempty"`
 }
@@ -1089,7 +1102,7 @@ type Cost struct {
 	CreatedAt string   `json:"createdAt,omitempty"`
 	CreatedBy string   `json:"createdBy,omitempty"`
 	Order     *Order   `json:"order,omitempty"`
-	UserId    int      `json:"userId,omitempty"`
+	UserID    int      `json:"userId,omitempty"`
 	Sites     []string `json:"sites,omitempty"`
 }
 
diff --git a/v5/types_test.go b/types_test.go
similarity index 98%
rename from v5/types_test.go
rename to types_test.go
index dc9e6db..93f1f94 100644
--- a/v5/types_test.go
+++ b/types_test.go
@@ -1,4 +1,4 @@
-package v5
+package retailcrm
 
 import (
 	"encoding/json"
diff --git a/v5/error.go b/v5/error.go
deleted file mode 100644
index cbdc9df..0000000
--- a/v5/error.go
+++ /dev/null
@@ -1,32 +0,0 @@
-package v5
-
-import "encoding/json"
-
-// APIErrorsList struct.
-type APIErrorsList map[string]string
-
-// APIError struct.
-type APIError struct {
-	SuccessfulResponse
-	ErrorMsg string        `json:"errorMsg,omitempty"`
-	Errors   APIErrorsList `json:"errors,omitempty"`
-}
-
-func (e *APIError) Error() string {
-	return e.ErrorMsg
-}
-
-func NewAPIError(dataResponse []byte) error {
-	a := &APIError{}
-
-	if len(dataResponse) > 0 && dataResponse[0] == '<' {
-		a.ErrorMsg = "Account does not exist."
-		return a
-	}
-
-	if err := json.Unmarshal(dataResponse, a); err != nil {
-		return err
-	}
-
-	return a
-}
diff --git a/v5/error_test.go b/v5/error_test.go
deleted file mode 100644
index 989b8e3..0000000
--- a/v5/error_test.go
+++ /dev/null
@@ -1,54 +0,0 @@
-package v5
-
-import (
-	"reflect"
-	"testing"
-
-	"golang.org/x/xerrors"
-)
-
-func TestFailure_ApiErrorsSlice(t *testing.T) {
-	b := []byte(`{"success": false,
-				"errorMsg": "Failed to activate module",
-				"errors": [
-					"Your account has insufficient funds to activate integration module",
-					"Test error"
-				]}`)
-	expected := APIErrorsList{
-		"0": "Your account has insufficient funds to activate integration module",
-		"1": "Test error",
-	}
-
-	var expEr *APIError
-	e := NewAPIError(b)
-
-	if xerrors.As(e, &expEr) {
-		if eq := reflect.DeepEqual(expEr.Errors, expected); eq != true {
-			t.Errorf("%+v", eq)
-		}
-	} else {
-		t.Errorf("Error must be type of APIError: %v", e)
-	}
-}
-
-func TestFailure_ApiErrorsMap(t *testing.T) {
-	b := []byte(`{"success": false,
-				"errorMsg": "Failed to activate module",
-				"errors": {"id": "ID must be an integer", "test": "Test error"}}`,
-	)
-	expected := APIErrorsList{
-		"id":   "ID must be an integer",
-		"test": "Test error",
-	}
-
-	var expEr *APIError
-	e := NewAPIError(b)
-
-	if xerrors.As(e, &expEr) {
-		if eq := reflect.DeepEqual(expEr.Errors, expected); eq != true {
-			t.Errorf("%+v", eq)
-		}
-	} else {
-		t.Errorf("Error must be type of APIError: %v", e)
-	}
-}
diff --git a/v5/marshaling.go b/v5/marshaling.go
deleted file mode 100644
index 15cfd50..0000000
--- a/v5/marshaling.go
+++ /dev/null
@@ -1,35 +0,0 @@
-package v5
-
-import (
-	"encoding/json"
-	"fmt"
-	"strconv"
-)
-
-func (t Tag) MarshalJSON() ([]byte, error) {
-	return json.Marshal(t.Name)
-}
-
-func (a *APIErrorsList) UnmarshalJSON(data []byte) error {
-	var i interface{}
-	var m map[string]string
-	if err := json.Unmarshal(data, &i); err != nil {
-		return err
-	}
-
-	switch e := i.(type) {
-	case map[string]interface{}:
-		m = make(map[string]string, len(e))
-		for idx, val := range e {
-			m[idx] = fmt.Sprint(val)
-		}
-	case []interface{}:
-		m = make(map[string]string, len(e))
-		for idx, val := range e {
-			m[strconv.Itoa(idx)] = fmt.Sprint(val)
-		}
-	}
-
-	*a = m
-	return nil
-}
diff --git a/v5/marshaling_test.go b/v5/marshaling_test.go
deleted file mode 100644
index 199b22a..0000000
--- a/v5/marshaling_test.go
+++ /dev/null
@@ -1,24 +0,0 @@
-package v5
-
-import (
-	"encoding/json"
-	"reflect"
-	"testing"
-)
-
-func TestTag_MarshalJSON(t *testing.T) {
-	tags := []Tag{
-		{"first", "#3e89b6", false},
-		{"second", "#ffa654", false},
-	}
-	names := []byte(`["first","second"]`)
-	str, err := json.Marshal(tags)
-
-	if err != nil {
-		t.Errorf("%v", err.Error())
-	}
-
-	if !reflect.DeepEqual(str, names) {
-		t.Errorf("Marshaled: %#v\nExpected: %#v\n", str, names)
-	}
-}