flutter-formdata上传头像

项目里用到与服务端交互图片，flutter formdata数据交互方法

 FormData formdata = FormData.fromMap(
          {"file": await MultipartFile.fromFile(path, filename: name)});
 Response response = await dio
          .post(baseUrl + UrlManager.uploadUserAvatar,
              data: formdata, options: options)
          .catchError((e) {

      });

之前在header里加了content-type,后来发现flutter如果判断是formdata的会帮我们进行content-type设置