'finish' 事件

发送响应时触发。 更具体地说，当响应头和正文的最后一段已移交给操作系统以通过网络传输时，则将触发此事件。 这并不意味着客户端已收到任何东西。

Emitted when the response has been sent. More specifically, this event is emitted when the last segment of the response headers and body have been handed off to the operating system for transmission over the network. It does not imply that the client has received anything yet.