Upload multi MultipartFile with params

[hakama99]

I have a feature, need to send multi file with params, it is wrong to use FormData.fromMap.

server will receive null on formFile

      var files = [];
      for (int i = 0; i < imgList.length; i++) {
        final element = imgList[i];
        final file = await MultipartFile.fromFile(element.path);
        var fileData = {
          "spec_id": element.spec_id,
          "name": element.name,
          "formfile": file,
        };
        files.add(fileData);
      }

      var sendData = {
        "files": files,
      };
      var formData = FormData.fromMap(sendData);

right way

      var formData = FormData();
      for (int i = 0; i < imgList.length; i++) {
        final element = imgList[i];
        final file = await MultipartFile.fromFile(element.path);
        formData.files.add(MapEntry("files[$i].formfile", file));
        formData.fields.add(MapEntry("files[$i].spec_id", element.spec_id));
        formData.fields.add(MapEntry("files[$i].name", element.name));
      }

server code