foo.dart

import 'dart:async';

class Game {
  String id = null;
  Duration tickDuration = const Duration(microseconds: (1000000 ~/ 60));
  DateTime updated = DateTime(0);
  Timer _timer = null;

  Game(String this.id);

  void update(Timer timer) {
    final now = DateTime.now();
    final delta = now.difference(updated);
    print(delta.inMicroseconds);
    updated = now;
  }

  void start() {
    print("Game '$id' started");
    _timer = Timer.periodic(tickDuration, update);
  }

  void stop() {
    print("Game '$id' ended");
    _timer?.cancel();
  }
}

void main() async {
  var game = Game("test")..start();

  await Future.delayed(Duration(seconds: 10));

  game.stop();
}