How do I use StreamedRequest in Dart http library to upload a file?

I want to upload a file via a non-multipart/form-data request like this:

POST http://127.0.0.1/upload
Cache-Control: no-cache

< /path/to/file/in/disk

(I tested and it successfully uploaded a file from JetBrain Rider's REST client to my REST endpoint.)

There is a StreamedRequest class in http package but I didn't find any constructor or setter to plug a byte stream or file content into it.

How do I use StreamedRequest to upload a file in Dart?

In some older code of mine I use

  /// Send a POST request to the Docker service.
  Future<http.ByteStream> _streamRequestStream(
      String path, Stream<List<int>> stream,
      {Map<String, String> query}) async {
    assert(stream != null);
    final url = serverReference.buildUri(path, query);
    final request = new http.StreamedRequest('POST', url)
      ..headers.addAll(headersTar);
    stream.listen(request.sink.add);
    final http.BaseResponse response =
        await request.send().then(http.Response.fromStream);
    if (response.statusCode < 200 || response.statusCode >= 300) {
      throw new DockerRemoteApiError(
          response.statusCode, response.reasonPhrase, null);
    }
    return (response as http.StreamedResponse).stream;
  }

which might do what you want

https://github.com/bwu-dart/bwu_docker/blob/master/lib/src/remote_api.dart#L160-L178

It uses the http package

import 'package:http/http.dart' as http;