It is possible for an os.Interrupt signal to be raised after
signals.RegisterCloser() and before startup of goroutine signals.Handle().
Race is prevented by synchronously calling signal.Notify().
This makes systemd not put unit into fail mode when stopping
INFO:
* make sure to use signals.RegisterCloser for everything that should be closed on interrupt
* for any net.Listeners created make sure to wrap them with network.WrapListener and register with signals.RegisterCloser
