diff --git a/playground/basic/address_test.go b/playground/basic/address_test.go
new file mode 100644
index 0000000..435c9d9
--- /dev/null
+++ b/playground/basic/address_test.go
@@ -0,0 +1,40 @@
+package basic
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestPrintAddress(t *testing.T) {
+	var a int
+	fmt.Printf("%T, %v, %p \n", a, a, &a)
+	passByVariable(a)
+	passByPointer(&a)
+}
+
+func passByVariable(a int) {
+	fmt.Printf("%T, %v, %p \n", a, a, &a)
+}
+
+func passByPointer(a *int) {
+	fmt.Printf("%T, %v, %p \n", a, a, &a)
+	fmt.Printf("%T, %v, %p \n", *a, *a, &*a)
+}
+
+type robot struct{}
+
+func TestStructAddress(t *testing.T) {
+	var a robot
+	fmt.Printf("%T, %v, %p \n", a, a, &a)
+	passStructByVariable(a)
+	passStructByPointer(&a)
+}
+
+func passStructByVariable(a robot) {
+	fmt.Printf("%T, %v, %p \n", a, a, &a)
+}
+
+func passStructByPointer(a *robot) {
+	fmt.Printf("%T, %v, %p \n", a, a, &a)
+	fmt.Printf("%T, %v, %p \n", *a, *a, &*a)
+}
diff --git a/playground/http/upload_test.go b/playground/http/upload_test.go
index 180c032..0081e10 100644
--- a/playground/http/upload_test.go
+++ b/playground/http/upload_test.go
@@ -30,7 +30,8 @@ func TestUploadFormFile(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if _, err = io.Copy(formFileWriter, bytes.NewReader(yamlFile)); err != nil {
+	_, err = io.Copy(formFileWriter, bytes.NewReader(yamlFile))
+	if err != nil {
 		t.Fatal(err)
 	}
 	writer.Close()