import 'dart:async';

import 'dart:io';

void main() async {

  for(int i = 0;i<10;i++)

  {

    async_func(((i%10 + 1) * 1000));

  }

  await sleep(15000);

}

Future pause(Duration d) => new Future.delayed(d);

Future sleep(int i) => new Future.delayed(Duration(milliseconds: i));

void async_func(int i) async {

  await sleep(i);

  var now = new DateTime.now();

  print("async_func ($i)\t($now)" );

}