Sample Dart program that handles `sigint`.

main.dart

// Copyright 2020 Google LLC.
// SPDX-License-Identifier: Apache-2.0

import 'dart:async';
import 'dart:io';

Future<void> main() async {
  var count = 0;
  ProcessSignal.sigint.watch().forEach((s) {
    count++;
    print('child: Got a SIGINT $count times, hit it 3 times to terminate');
    if (count >= 3) {
      exit(0);
    }
  });
  print('child: Sleep 5s');
  await Future.delayed(Duration(seconds: 5));
  print('child: 5 sec done.');
  exit(55);
}