Golbat evolves into Crobat with high happiness (aka friendship). It sounds like you're using Pokemon Refresh, which increases "affection", not happiness which is a separate thing.
Happiness is increased by keeping the Pokemon in your party, battling, not letting it faint. But the best way is to let it hold a Soothe Bell, which increases happiness as you walk around. If Golbat is level 39 already you are probably close, give it the Soothe Bell and it should evolve in a few more levels.