I overheard in a subway train two young people were in a dialogue A:出了地铁就是XX电影院了，你是去呢还是去呢？ B：我去。 What does "你是去呢还是去呢" mean?
It's kind of a joke. There could be a few reasons:
The girl thought her friend really want to go to the cinema but perhaps he was not willing to admit the fact he was really wanting to (especially with her I guess) maybe because he felt awkward/shy to be known the fact. The girl was trying to reveal his pretending.
It could also be that she was simply just wanting him to go to the cinema by providing only choice as if saying go to the cinema, there is no other choice.
She was guessing he would go to the cinema based on her understanding about her friend.
There could be other reasons according to context.
The pattern could go on and on like 你是去呢, 还是去呢, 还是去呢... ....
No meaning and does not make sense. I think you missed a word in the sentence, 你是去呢还是"不"去呢? - Are you going (去) or not going (不去)?
It could be a casual conservation that one who has jokingly placed a question to trick his friend into confusion and returns the answer the way he wants/designed - as 去 is the only choice :)
Well, "X or Y" is to give a choice to choose. This is the same usage for both English and Chinese. A trending usage (jokingly) in oral Chinese is to make the choices the same, so the one who needs to make the choice doesn't have a choice. The one (A) who said that definitely wants B to go, but presented in a way that a choice is given.