dart - [SEVERE] 非同期エラーの後、DartAngular アプリがビルドされない

Question

dart SDK 2.5.0-stable にアップグレードしました。実行後pub global run webdev serve web:8081 --auto=refresh --release、深刻なエラーが発生します。このバージョンで重大な変更が導入されたことは知っていますが、変更ログを読んだ後でも、それを修正する方法がわかりません。

[INFO] Building new asset graph completed, took 2.3s
[INFO] Checking for unexpected pre-existing outputs. completed, took 1ms
[INFO] Serving `web` on http://127.0.0.1:8081
[SEVERE] ERROR - 2019-09-12 09:19:11.608930
[SEVERE] Asynchronous error
[SEVERE] type '_WebSocketProtocolTransformer' is not a subtype of type 'StreamTransformer<Uint8List, dynamic>' of 'streamTransformer'
[SEVERE] dart:async                                                       Stream.transform
[SEVERE] package:web_socket_channel/src/copy/web_socket_impl.dart 712:28  new WebSocketImpl.fromSocket
[SEVERE] package:web_socket_channel/src/channel.dart 94:36                new WebSocketChannel
[SEVERE] package:shelf_web_socket/src/web_socket_handler.dart 82:15       WebSocketHandler.handle.<fn>
[SEVERE]