RetryClient doesn't work in isolates

[predatorx7]

We cannot use RetryClient in Isolate.run because of the use of StreamController in StreamedRequest for making a copy of requests.

Example

main.dart

import 'dart:isolate';

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

import 'test_server.dart';

void main() async {
  final server = await startTestHttpServer();

  Future<void> _testPost(Client Function() clientFactory, String host) async {
    await Isolate.run(
      () => clientFactory().post(
        Uri.http(host, '/hello'),
        body: 'Hello World!',
      ),
    );
  }

  await _testPost(() => RetryClient(Client()), server.uri.authority);

  server.server.close();
}

test_server.dart

import 'dart:io';

import 'package:shelf_router/shelf_router.dart';
import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart' as io;
import 'package:http/http.dart' as http;

typedef TestServer = ({HttpServer server, Uri uri});

Future<TestServer> startTestHttpServer(
  void Function(Router router) onRouter,
) async {
  var app = Router();

   app.post('/hello', (Request request) {
      return Response.ok('ok');
    });

  final server = await io.serve(app, 'localhost', 8080);

  final serverUri = Uri.http('${server.address.host}:${server.port}');

  return (server: server, uri: serverUri);
}

Error Logs

Unhandled exception:
Invalid argument:  <- Instance of '_SyncStreamController<List<int>>' (from dart:async)
 <- Instance of 'StreamedRequest' (from package:http/src/streamed_request.dart)
 <- Instance of 'Response' (from package:http/src/response.dart)
 <- _List len:1 (from dart:core)
is unsendable object (see restrictions listed at`SendPort.send()` documentation for more information): Instance of 'Future<void>'
#0      Isolate._exit (dart:isolate-patch/isolate_patch.dart:647:75)
#1      Isolate.exit (dart:isolate-patch/isolate_patch.dart:650:5)
#2      _RemoteRunner._run (dart:isolate:1031:13)
<asynchronous suspension>