diff --git a/.example/other/test.go b/.example/other/test.go
index fabb90ff8..67760c9c5 100644
--- a/.example/other/test.go
+++ b/.example/other/test.go
@@ -13,10 +13,6 @@ type TokenRequest struct {
 }
 
 func main() {
-	s := "123456"
-	fmt.Println(s[0:2])
-	fmt.Println(s[1:3])
-	return
 	//	s := `
 	//{
 	//  "policy": {"name":"john"},
diff --git a/util/gconv/gconv.go b/util/gconv/gconv.go
index e9e028b25..f694aeb76 100644
--- a/util/gconv/gconv.go
+++ b/util/gconv/gconv.go
@@ -379,11 +379,13 @@ func Int64(i interface{}) int64 {
 	default:
 		s := String(value)
 		isMinus := false
-		if s[0] == '-' {
-			isMinus = true
-			s = s[1:]
-		} else if s[0] == '+' {
-			s = s[1:]
+		if len(s) > 0 {
+			if s[0] == '-' {
+				isMinus = true
+				s = s[1:]
+			} else if s[0] == '+' {
+				s = s[1:]
+			}
 		}
 		// Hexadecimal
 		if len(s) > 2 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X') {
diff --git a/util/gconv/gconv_map.go b/util/gconv/gconv_map.go
index 33163b34e..63a6b47d7 100644
--- a/util/gconv/gconv_map.go
+++ b/util/gconv/gconv_map.go
@@ -51,11 +51,19 @@ func doMapConvert(value interface{}, recursive bool, tags ...string) map[string]
 		switch r := value.(type) {
 		case string:
 			if len(r) > 0 && r[0] == '{' && r[len(r)-1] == '}' {
-				json.Unmarshal([]byte(r), &m)
+				if err := json.Unmarshal([]byte(r), &m); err != nil {
+					return nil
+				}
+			} else {
+				return nil
 			}
 		case []byte:
 			if len(r) > 0 && r[0] == '{' && r[len(r)-1] == '}' {
-				json.Unmarshal(r, &m)
+				if err := json.Unmarshal(r, &m); err != nil {
+					return nil
+				}
+			} else {
+				return nil
 			}
 		case map[interface{}]interface{}:
 			for k, v := range r {
diff --git a/util/gconv/gconv_struct.go b/util/gconv/gconv_struct.go
index 47ba66ece..c2ffb1cfe 100644
--- a/util/gconv/gconv_struct.go
+++ b/util/gconv/gconv_struct.go
@@ -253,7 +253,8 @@ func bindVarToReflectValue(structFieldValue reflect.Value, value interface{}) (e
 		if err := Struct(value, structFieldValue); err != nil {
 			structFieldValue.Set(reflect.ValueOf(value))
 		}
-
+	// Note that the slice element might be type of struct,
+	// so it uses Struct function doing the converting internally.
 	case reflect.Slice, reflect.Array:
 		a := reflect.Value{}
 		v := reflect.ValueOf(value)