dispose method

Future<void> dispose()

销毁线程池，正在执行的任务不一定会立即被销毁，当前任务执行完成后才会被销毁

Implementation

Future<void> dispose() async {
  // 停止所有的线程
  _printf("dispose all isolate");
  for (var isolate in _isolates) {
    final completer = Completer<String?>();
    _iTask.sendTask(
        () async {
          return ISOLATE_DISPOSE;
        },
        isolate,
        (message) {
          completer.complete(message);
          _destroy();
        });
  }
}