Yiqings-MacBook-Pro:~ xzkuku$ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.5.4-hotfix.2, on Mac OS X 10.14.5 18F132, locale en-CN)
⣻Unhandled exception:
Bad state: Future already completed
#0      _AsyncCompleter.complete (dart:async/future_impl.dart:39:31)
#1      _NativeSocket.startConnect.<anonymous closure>.connectNext.<anonymous closure> (dart:io-patch/socket_patch.dart:508:23)
#2      _NativeSocket.issueWriteEvent.issue (dart:io-patch/socket_patch.dart:862:14)
#3      _NativeSocket.issueWriteEvent (dart:io-patch/socket_patch.dart:869:12)
#4      _NativeSocket.multiplex (dart:io-patch/socket_patch.dart:890:11)
#5      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:171:12)