Peeing fantasy

So the new guy I started playing with is a complete dom. I knew he was kinky when we met, but I didn’t realise HOW kinky. He’s pretty much done everything before - threesomes, swingers parties, cuckholding and everything in between. Our first time together he was super rough (in a good way), with some hair pulling, pussy slapping, choking, gagging, restraining (just with his hands - he didn’t bring any toys)...... it was mind blowing for me. Then he shared that he only has one fantasy: for me to pee on him.

I’ve never done anything like that before and I’m just wondering - how?? And when?? And where?? Cuz it’s not like I can really control when I need to pee... plus I have a habit of going before sex anyway to make sure that I DON’T accidentally pee...... so please someone tell me how the golden shower is supposed to work?