Optionaltimeout: numberMaximum time in ms the client should wait to flush its event queue before shutting down. Omitting this parameter will cause the client to wait until all events are sent before disabling itself.
A promise which resolves to true if the queue successfully drains before the timeout, or false if it
doesn't (or if there's no client defined).
Call
close()on the current client, if there is one. See Client.close.