Demo for understanding dart async.

dart_async_demo.dart

import 'dart:async';

main() {
  Future(() => print('Line 1'));
  scheduleMicrotask(() => print('Line 2'));
  print('Line 3');
  print('Line 4');
  Future(() {
    Future(() => print('Line 5'));
    scheduleMicrotask(() => print('Line 6'));
    print('Line 7');
  });
  print('Line 8');
  scheduleMicrotask(() {
    print('Line 9');
    Future(() => print('Line 10'));
    scheduleMicrotask(() => print('Line 11'));
  });
  print('Line 12');
  dummy1();
  print('Line 14');
  Future(() => print('Line 15'));
  scheduleMicrotask(() => print('Line 16'));
  dummy2();
  print('Line 17');
}

void dummy1() {
  print('Line dummy1 1');
  Future(() => print('Line dummy1 2'));
  scheduleMicrotask(() => print('Line dummy1 3'));
  print('Line dummy1 4');
  scheduleMicrotask(() => print('Line dummy1 5'));
  Future(() => print('Line dummy1 6'));
}

void dummy2() {
  print('Line dummy2 1');
  Future(() => print('Line dummy2 2'));
  scheduleMicrotask(() => print('Line dummy2 3'));
  print('Line dummy2 4');
  scheduleMicrotask(() => print('Line dummy2 5'));
  Future(() => print('Line dummy2 6'));
}

View result online from:

https://dartpad.dev/6932e97422af3268569d9e6c002b263e