Generate route with prefix (#1200)

* Generate route with prefix

* Update api convert

* Remove TrimSpace

* Update path join

* Format code

* Format code

Co-authored-by: anqiansong <anqiansong@bytedance.com>

tools/goctl/api/dartgen/gen.go

@@ -25,6 +25,7 @@ func DartCommand(c *cli.Context) error {
 		return err
 	}
 
+	api.Service = api.Service.JoinPrefix()
 	if !strings.HasSuffix(dir, "/") {
 		dir = dir + "/"
 	}