Should I take part in Erasmus or quit my job at home? Don't know what to do?

I'm considering taking part in a 3 month work based Erasmus programme in Italy with my university. The only issue is that I'd most likely have to quit my job to do it. It took me a long time to find a job that fit around my university schedule and I don't want to lose it because I'm getting some experience and money. It is only a bar work/waitressing job, but a job nevertheless. Erasmus at my university isn't paid for like some European programmes so I'd have to take everything I've saved.

I've wanted to do Erasmus since I started uni almost 2 years ago but never could due to finances, now I can afford to go but I'll probably have to quit my job and be back at square one when the programme ends (I can't imagine any employer keeping a position open for 3 months unless it was a medical issue ). I'm torn because on the one hand, I'd be getting valuable experience in a job that I actually want to do when I graduate and I'd get experience living abroad. And on the other hand, I'd be losing my job and end up being broke again when I got back.

Both of those are incredibly important to me because I want to live in Italy teaching English as a Foreign Language after uni and that's what my placement on Erasmus would be.

I haven't mentioned anything to my boss yet because I'm not sure on what to do. Some people have told me their boss would keep their job open if they were doing a similar thing and others have said it's highly unlikely they'd keep my job until I came back.

Sorry about the essay! I want to give you as much information as possible. What would you do if you was in this situation? I'm really stuck