Wrapped errors with xerrors

go.mod

@@ -4,4 +4,5 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/stretchr/testify v1.2.2
+	golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7
 )

go.sum

@@ -4,3 +4,5 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7 h1:9zdDQZ7Thm29KFXgAX/+yaf3eVbP7djjWp/dXAppNCc=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

messenger.go

@@ -10,6 +10,8 @@ import (
 	"net/http"
 	"strings"
 	"time"
+
+	"golang.org/x/xerrors"
 )
 
 const (
@@ -192,11 +194,11 @@ func (m *Messenger) ProfileByID(id int64, profileFields []string) (Profile, erro
 		qr := QueryResponse{}
 		err = json.Unmarshal(content, &qr)
 		if qr.Error != nil {
-			err = fmt.Errorf("facebook error: %s", qr.Error.Message)
+			return p, xerrors.Errorf("facebook error: %w", qr.Error)
 		}
 	}
 
-	return p, err
+	return p, nil
 }
 
 // GreetingSetting sends settings for greeting
@@ -279,13 +281,14 @@ func (m *Messenger) handle(w http.ResponseWriter, r *http.Request) {
 
 	err := json.Unmarshal(body, &rec)
 	if err != nil {
-		fmt.Println("could not decode response:", err)
+		err = xerrors.Errorf("could not decode response: %w", err)
+		fmt.Println(err)
 		fmt.Fprintln(w, `{status: 'not ok'}`)
 		return
 	}
 
 	if rec.Object != "page" {
-		fmt.Println("Object is not page, undefined behaviour. Got", rec.Object)
+		fmt.Println("object is not page, undefined behaviour. Got", rec.Object)
 	}
 
 	if m.verify {
@@ -304,22 +307,22 @@ func (m *Messenger) handle(w http.ResponseWriter, r *http.Request) {
 // checkIntegrity checks the integrity of the requests received
 func (m *Messenger) checkIntegrity(r *http.Request) error {
 	if m.appSecret == "" {
-		return fmt.Errorf("missing app secret")
+		return xerrors.New("missing app secret")
 	}
 
 	sigHeader := "X-Hub-Signature"
 	sig := strings.SplitN(r.Header.Get(sigHeader), "=", 2)
 	if len(sig) == 1 {
 		if sig[0] == "" {
-			return fmt.Errorf("missing %s header", sigHeader)
+			return xerrors.Errorf("missing %s header", sigHeader)
 		}
-		return fmt.Errorf("malformed %s header: %v", sigHeader, strings.Join(sig, "="))
+		return xerrors.Errorf("malformed %s header: %v", sigHeader, strings.Join(sig, "="))
 	}
 
 	checkSHA1 := func(body []byte, hash string) error {
 		mac := hmac.New(sha1.New, []byte(m.appSecret))
 		if mac.Write(body); fmt.Sprintf("%x", mac.Sum(nil)) != hash {
-			return fmt.Errorf("invalid signature: %s", hash)
+			return xerrors.Errorf("invalid signature: %s", hash)
 		}
 		return nil
 	}
@@ -333,7 +336,7 @@ func (m *Messenger) checkIntegrity(r *http.Request) error {
 	case "sha1":
 		return checkSHA1(body, sigHash)
 	default:
-		return fmt.Errorf("unknown %s header encoding, expected sha1: %s", sigHeader, sig[0])
+		return xerrors.Errorf("unknown %s header encoding, expected sha1: %s", sigHeader, sig[0])
 	}
 }
 

response.go

@@ -12,6 +12,8 @@ import (
 	"net/http"
 	"net/textproto"
 	"strings"
+
+	"golang.org/x/xerrors"
 )
 
 // AttachmentType is attachment type.
@@ -72,17 +74,21 @@ type QueryError struct {
 	FBTraceID string `json:"fbtrace_id"`
 }
 
+// QueryError implements error
+func (e QueryError) Error() string {
+	return e.Message
+}
+
 func checkFacebookError(r io.Reader) error {
 	var err error
 
 	qr := QueryResponse{}
 	err = json.NewDecoder(r).Decode(&qr)
 	if err != nil {
-		return fmt.Errorf("json unmarshal error: %s", err)
+		return xerrors.Errorf("json unmarshal error: %w", err)
 	}
 	if qr.Error != nil {
-		err = fmt.Errorf("facebook error: %s", qr.Error.Message)
-		return err
+		return xerrors.Errorf("facebook error: %w", qr.Error)
 	}
 
 	return nil