I've learned in school that 'go' is a momentary verb, which normally cannot be used with 'for + time period'. No, this isn't true. Of course you can say that you 'Go (somewhere) for ( a length of) time'. It tells us the amount of time that you are spending or have spent in that place. In fact, the whole concept of momentary verbs is unhelpful to the student. I just looked at one of the few grammar websites which bothers to mention them, and I found the list hit, knock, jump and kick. Well, you can obviously do all of these actions for a certain time: "He kicked the ball for a while" "I knocked on the door for 30 seconds" and so on. If I were you, I would forget about this so-called rule.