Spawning Isolates in Dart

Isolates

import 'dart:io';
import 'dart:async';
import 'dart:isolate';

Isolate isolate;
main() async{
stdout.writeln('spawning isolate...');
await start();
stdout.writeln('press enter key to quit...');
await stdin.first;
stop();
stdout.writeln('goodbye!');
exit(0);
}



void start() async {
  ReceivePort receivePort= ReceivePort(); //port for this main isolate to receive messages.
  isolate = await Isolate.spawn(runTimer, receivePort.sendPort);
  receivePort.listen((data) {
    stdout.write('RECEIVE: ' + data + ', ');
  });
}

void runTimer(SendPort sendPort) {
  int counter = 0;
  Timer.periodic(new Duration(seconds: 1), (Timer t) {
    counter++;
    String msg = 'notification ' + counter.toString();
    stdout.write('SEND: ' + msg + ' - ');
    sendPort.send(msg);
  });
}

void stop() {
  if (isolate != null) {
    stdout.writeln('killing isolate');
    isolate.kill(priority: Isolate.immediate);
    isolate = null;
  }
}