AddListener is used to append the input ShutdownListener to the internal list which will be used for notification.

GetShutdownHandler can be invoked from other packages for fetching an instance of the ShutdownHandler.

Wait Blocks the calling thread and waits till the shutdown notification is received.

ShutdownHandler is responsible for listening to shutdown notifications and propagate the same.

ShutdownListener should be implemented by structs which needs shutdown notification.