如何在Dart中发出OPTIONS请求？

import 'dart:io';

void main() async {
  var client = HttpClient();
  var request = await client.openUrl('OPTIONS', Uri.parse('https://example.com'));
  var response = await request.close();

  print('Response status code: ${response.statusCode}');
  print('Response headers: ${response.headers}');
  await response.drain();
  client.close();
}