delay method Null safety

Future delay(
  1. [FutureOr callback(

    Utility to delay some callback (or code execution). TODO: Add a separated implementation of delay() with the ability to stop it.


    void main() async {
      print('+ wait for 2 seconds');
      await 2.delay();
      print('- 2 seconds completed');
      print('+ callback in 1.2sec');
      1.delay(() => print('- 1.2sec callback called'));
      print('currently running callback 1.2sec');


    Future delay([FutureOr callback()?]) async => Future.delayed(
          Duration(milliseconds: (this * 1000).round()),