http2stream.rstCode
设置为 RST_STREAM 错误代码在从连接的对等方接收到 RST_STREAM 帧、调用 http2stream.close() 或 http2stream.destroy() 后销毁 Http2Stream 时报告。
如果 Http2Stream 尚未关闭,则为 undefined。
Set to the RST_STREAM error code reported when the Http2Stream is
destroyed after either receiving an RST_STREAM frame from the connected peer,
calling http2stream.close(), or http2stream.destroy(). Will be
undefined if the Http2Stream has not been closed.