Expose KillerSubscriber & SubscribeWithKiller function to allow graceful stop of an app when the following signals are triggered:
- os.Kill
- os.Interrupt
- syscall.SIGHUP
- syscall.SIGTERM
- syscall.SIGQUIT
- syscall.SIGSTOP
also allow killing an app after a second stop signal is triggered (ex: 2x
ctr+c)