The problem of generating API by gin-swagger

as the title: gin cooperates with swagger to generate restful api documents. But the rendering result is a little different from the imagination.

...
...
"parameters": [
                    {
                        "type": "file",
                        "description": "",
                        "name": "email",
                        "in": "formData",
                        "required": true
                    },
                    {
                        "type": "file",
                        "description": "",
                        "name": "username",
                        "in": "formData",
                        "required": true
                    },
                    {
                        "type": "file",
                        "description": "",
                        "name": "password",
                        "in": "formData",
                        "required": true
                    }
                ],
                ...
                ...

Why is the format different before and after generation?