anchor.diff:  /// https://github.com/dart-lang/sdk/issues/34656
   Stream<T> convertBroadcastToSingleSubscriber<T>(Stream<T> stream) {
     final StreamController<T> controller = StreamController<T>();
  -  StreamSubscription<T> subscription;
  +  late StreamSubscription<T> subscription;
     controller.onListen =
         () => subscription = stream.listen((T e) => controller.add(e));
     controller.onCancel = () => subscription.cancel();
  
positive.code: // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // @dart=2.9
  
  import 'dart:async';
  
  
negative.code:       ? uri.replace(scheme: 'http')
        : uri.replace(scheme: 'https');
    final client = SseClient('$uri');
    final Stream<String>? stream =
        client.stream?.asBroadcastStream() as Stream<String>?;
    final service = VmServiceWrapper.fromNewVmService(
      stream,
      client.sink!.add,
      uri,
    );
  
    unawaited(client.sink?.done.whenComplete(() {
      finishedCompleter.complete();
      service.dispose();
    }));
    serviceCompleter.complete(service);
  
    unawaited(stream?.drain().catchError(onError));
    return serviceCompleter.future;
  }
  
  