Posting File over http with Flutter(dart)

I am developing a flutter application with Servicestack .net Rest API service. And i am stuck with calling and uploading files through api on flutter side, there are solutions with dart:http libraries (MultipartRequest), but they are not compatible with servicestack client, cause you are using HttpClientRequest when creating a request…what is the solution?

Use Dart’s dart:http Library to upload files directly to your ServiceStack Service, i.e. don’t use ServiceStack’s dart JsonServiceClient.