事件：'trailers'

🌐 Event: 'trailers'

• headers <HTTP/2 Headers Object> 描述头部的对象
• flags <number> 相关的数字标志
• rawHeaders HTTP/2 Raw Headers

'trailers' 事件在接收到与尾随头字段关联的头块时触发。监听器回调会传入 HTTP/2 头对象、与头关联的标志，以及原始格式的头（见 HTTP/2 原始头）。

🌐 The 'trailers' event is emitted when a block of headers associated with trailing header fields is received. The listener callback is passed the HTTP/2 Headers Object, flags associated with the headers, and the headers in raw format (see HTTP/2 Raw Headers).

如果在接收到尾部信息之前调用了 http2stream.end()，并且没有读取或监听传入的数据，则此事件可能不会被触发。

🌐 This event might not be emitted if http2stream.end() is called before trailers are received and the incoming data is not being read or listened for.

stream.on('trailers', (headers, flags) => {
  console.log(headers);
}); 拷贝