'disconnect' 事件

如果 Node.js 进程是使用 IPC 通道衍生（参见子进程和集群文档），则在 IPC 通道关闭时将触发 'disconnect' 事件。

If the Node.js process is spawned with an IPC channel (see the Child Process and Cluster documentation), the 'disconnect' event will be emitted when the IPC channel is closed.