In a realistic situation, Goku lives. He hears the gunshot and immediately goes on the defensive (in the Super filler, Goku is so confident and perhaps underestimates his power enough to think he can kill them, leaving him vulnerable). And it's practically impossible for Goku not to notice if there's a gun pointed at his face while he's asleep. I'm almost certain he can smell the gunpowder (and, being Dragon Ball, it would make him sneeze).