fix bug with pointer

sender/structs.go

@@ -121,7 +121,7 @@ func (cm *CustomerMessage) GetToUser() interface{} {
 	return cm.Touser
 }
 
-func (cm *CustomerMessage) GetPreview() interface{} {
+func (cm *CustomerMessage) GetPreview() bool {
 	return cm.Preview
 }
 

sender/wrapper.go

@@ -15,18 +15,18 @@ func Sender(accessToken string, message MessageStruct) (int, string) {
 	switch message.MessageType {
 	case "CUSTOMER":
 	case "MASS":
-		var cmi CustomerMessageInterface
+		var cmi TextCustomerMessage
 		err := json.Unmarshal(message.MessageData, &cmi)
 
 		if err != nil {
-			msg := "Unmarshal CustomerMessageInterface failed"
+			msg := "Unmarshal TextCustomerMessage failed"
 			log.
 				WithField("error", err).
 				Error(msg)
 			return -10001, msg
 		}
 
-		return CustomerMessageSender(accessToken, cmi)
+		return CustomerMessageSender(accessToken, &cmi)
 	case "TEMPLATE":
 		var tm TemplateMessage
 		err := json.Unmarshal(message.MessageData, &tm)