cluster.fork([env])

• env <Object> 要添加到工作进程环境变量的键/值对。
• 返回: <cluster.Worker>

衍生新的工作进程。

这只能从主进程调用。

• env <Object> Key/value pairs to add to worker process environment.
• Returns: <cluster.Worker>

Spawn a new worker process.

This can only be called from the primary process.