Synchronous in dart

dart_synchronous.dart

import 'dart:async';
import 'dart:io';
import 'package:synchronized/extension.dart';

main() async {
  var demo = Demo();

  await demo.runSynchronized();
  await demo.runNotSynchronized();
}

class Demo {
  Future runNotSynchronized() async {
    stdout.writeln('not synchronized');
    write1234();
    write1234();
    await Future.delayed(const Duration(milliseconds: 300));
    stdout.writeln();
  }

  Future runSynchronized() async {
    stdout.writeln('synchronized');
    synchronized(() async {
      await write1234();
    });
    synchronized(write1234);
    await Future.delayed(const Duration(milliseconds: 300));
    stdout.writeln();
  }

  Future write1234() async {
    for (var value in [1, 2, 3, 4]) {
      await Future.delayed(const Duration(milliseconds: 30));
      stdout.write(value);
    }
  }
}