[DART] Future 클래스 : then 메소드 사용하기

import 'dart:async';

void main() async {
  await printWithDelay('테스트1');
  await printWithDelay('테스트2');
  await printWithDelay('테스트3');
}

const Duration duration = Duration(seconds: 1);

Future<void> printWithDelay(String message) {
  return Future.delayed(duration).then((_) {
    print(message);
  });
}