Goku can breath in space dude. When he fought Beerus he left God mode when they were fighting in the cave. Most of that battle he wasn't fighting in his God form. Obviously you didn't pay attention. It was also stated that he retained a lot of the power from the God state, and since he wasn't in his God form, yet he was in space talking and breathing just fine, I'd say that obviously one of the powers he gained was the ability to function in space.