it's not a 100% detection. You can certainly pile up deadlocked go routines, but the way most libraries (including the standard library) are setup, if you were to write some server, you'd only deadlock on the request but the app keep running. There is no way to reliably detect that but the service will probably service most requests if you didn't plain deadlock everything.

If all go routines are deadlocked, the runtime will terminate the service.

It's a kind of graceful and somewhat safe degradation.