add checkout handler

message-handler.go

@@ -15,12 +15,13 @@ var Handlers = map[uint16]MessageHandler{
 	SetDeliveryType:         &SetDeliveryHandler{},
 	RemoveItemType:          &RemoveItemHandler{},
 	RemoveDeliveryType:      &RemoveDeliveryHandler{},
+	CreateCheckoutOrderType: &CheckoutHandler{},
 }
 
 func GetMessageHandler(t uint16) (MessageHandler, error) {
 	h, ok := Handlers[t]
 	if !ok {
-		return nil, fmt.Errorf("no handler for type %d", t)
+		return nil, fmt.Errorf("no handler for message type %d", t)
 	}
 	return h, nil
 }