i have the same problem ...

IBOOK:teste $ flutter pub get Unhandled exception:
Bad state: Future already completed
#0 _AsyncCompleter.complete (dart:async/future_impl.dart:42:31)
#1 _NativeSocket.startConnect..connectNext. (dart:io-patch/socket_patch.dart:642:23) #2 _NativeSocket.issueWriteEvent.issue (dart:io-patch/socket_patch.dart:1045:14) #3 _NativeSocket.issueWriteEvent (dart:io-patch/socket_patch.dart:1052:12) #4 _NativeSocket.multiplex (dart:io-patch/socket_patch.dart:1073:11) #5 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12) Running "flutter pub get" in teste...
pub get failed (255; #5 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12))