main.dart

import 'package:async/async.dart';

Future<void> main() async {
  final operation = CancelableOperation.fromFuture(parentFuture());
  await Future.delayed(Duration(seconds: 2));
  await operation.cancel();
  print('canceled');
}

parentFuture() async {
  await childFuture();
  await childFuture();
  await childFuture();
  await childFuture();
}

childFuture() async {
  await Future.delayed(Duration(seconds: 2));
  print('executed');
}