为什么server.maxHeadersCount为空?

我创建简单服务器

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('okay');
});
console.log(server.maxHeadersCount) // expected is 2000, actual is null

In this section of docs 它说 server.maxHeadersCount