fix auto migrate

crud.go

@@ -132,6 +132,10 @@ func (crud *CRUD) Attach(model Model, ops ...Option) (err error) {
 	if opts.DB == nil {
 		opts.DB = crud.db
 	}
+	//auto migrate database struct
+	if err = crud.db.AutoMigrate(model); err != nil {
+		return
+	}
 	//migrate table schema
 	if err = migrateUp("", model); err != nil {
 		return