anchor.diff:  
     /// Attempt to retrieve the isolate with id [isolateId], or `null` if it has
     /// been collected.
  -  Future<vm_service.Isolate> getIsolateOrNull(String isolateId) {
  +  Future<vm_service.Isolate> getIsolateOrNull(String isolateId) async {
       return service.getIsolate(isolateId)
         .catchError((dynamic error, StackTrace stackTrace) {
           return null;
  
positive.code:   while (socket == null) {
      attempts += 1;
      try {
        socket = await constructor(url, compression: compression);
      } on io.WebSocketException catch (e) {
        await handleError(e);
      } on io.SocketException catch (e) {
  
negative.code:     isolateEvents = service.onIsolateEvent.listen((vm_service.Event event) {
        if (event.kind == vm_service.EventKind.kServiceExtensionAdded
            && event.extensionRPC == extensionName) {
          isolateEvents?.cancel();
          extensionAdded.complete(event.isolate);
        }
      });
  