If you go to "gaye sag", It means that you face a very bad problem that will get you fucked.(mostly used in Farsi but It is also used in English)
(Its apparent meaning is "getting fucked by a dog")
a: What will happen?
b: I will go to "gaye sag"!
In persian when someone is dealing with a hard situation this phrase is used
for example when someone is experienced a very bad and tough times in a relation ship in persian we say that person have gone to "gaye sag"