注意 :authority 和 host

HTTP/2 要求请求具有 :authority 伪标头或 host 标头。 当直接构建 HTTP/2 请求时首选 :authority，从 HTTP/1 转换时首选 host（例如在代理中）。

如果 :authority 不存在，则兼容性 API 将回退到 host。 有关详细信息，请参阅 request.authority。 但是，如果不使用兼容性 API（或直接使用 req.headers），则需要自己实现任何回退行为。

HTTP/2 requires requests to have either the :authority pseudo-header or the host header. Prefer :authority when constructing an HTTP/2 request directly, and host when converting from HTTP/1 (in proxies, for instance).

The compatibility API falls back to host if :authority is not present. See request.authority for more information. However, if you don't use the compatibility API (or use req.headers directly), you need to implement any fall-back behavior yourself.