make future timer in dart

future_timer.dart

import 'dart:async';

void main() async {
  for (int i = 0; i < 5; i++) {
    String result = await makeFutureTimer(
      duration: Duration(seconds: 0),
      action: () {
        print(DateTime.now());
        return 'RETURN VALUE $i';
      },
    );
    print(result);
  }

  List<Future> requests = [];
  for (int j = 0; j < 5; j++) {
    requests.add(makeFutureTimer(
      duration: Duration(seconds: 1),
      action: () {
        print(DateTime.now());
        return 'RETURN VALUE $j';
      },
    ),);
  }
  
  var multipleResult = await Future.wait(requests)  ;
  print(multipleResult);
}

Future makeFutureTimer({Duration duration, Function action}) {
  final Completer completer = Completer();
  Timer(duration, () {
    String returnValue = action();
    completer.complete(returnValue);
  });
  return completer.future;
}