import "dart:async";

Future<DateTime> currentTime(int forExp) async {
  DateTime now;
  for (int i = 0; i < 3; i++) {
    now = new DateTime.now();
    print("- exp${forExp}:current-time[${i}] = ${now}");
  }
  return now;
}

Future<Object> exp1() async {
  print("* exp1:start");
  DateTime now = await currentTime(1);
  print("* exp1:result=${now}");
  return null;
}

Future<Object> exp2() async {
  print("* exp2:start");
  Future<Object> result = currentTime(2);
  result
    ..then((DateTime now) {
      print("* exp2:result=${now}");
    })
    ..whenComplete(() {
      print("* exp2:complete");
    });
  print("* exp2:reaching-flow-end");
  return result;
}

void main() {
  Future.wait([exp1(), exp2()]).whenComplete(() {
    print("all future complete");
  });
  print("reach end of main function");
}