Async Dart

main.dart

void main() async {
  
  final delayed3 = Future.delayed(
    const Duration(seconds: 3),
    () => '3',
  );

  
  final delayed2 = Future.delayed(
    const Duration(seconds: 2),
    () => '2',
  );
  
  final delayed1 = Future.delayed(
    const Duration(seconds: 1),
    () => '1',
  );
  
  await Future.wait([
    delayed3.then(print),
    delayed2.then(print),
    delayed1.then(print)
  ]);
}