anchor.diff:    final ReceivePort exitPort = ReceivePort();
     final ReceivePort errorPort = ReceivePort();
     Timeline.finishSync();
  -  final Isolate isolate = await Isolate.spawn<_IsolateConfiguration<Q, FutureOr<R>>>(
  +  await Isolate.spawn<_IsolateConfiguration<Q, FutureOr<R>>>(
       _spawn,
       _IsolateConfiguration<Q, FutureOr<R>>(
         callback,
  
positive.code:   resultPort.close();
    exitPort.close();
    errorPort.close();
    isolate.kill();
    Timeline.finishSync();
    return result.future;
  }
  
negative.code:     flow: Flow.step(configuration.flowId),
    );
    Timeline.timeSync(
      '${configuration.debugLabel}: exiting and returning a result', () {},
      flow: Flow.step(configuration.flowId),
    );
    Isolate.exit(configuration.resultPort, result);
  }
  