How Long Does It Take For A Golbat To Evolve. With High Friendship I Know But How Long Does It Take?

Depends on what the lady says if he is close to you and she tells you that in can evolve in 1-5 levels

with that being said if you have unlimited rare candies you can give them to him until it evolves

It should take about  1-6 lvl.You can either fight against trainer or Pokemon or use rare candies.
Personally I had a golbat lvl 22 it evolved into crobat in lvl24.Good luck.