Are you coming or not? - is possible translation, I think And it's more appropriate to use word which starts with consonant after vowel: Ви Йдете чи ні?
"To be going to" as far as I understand is used to speak about future plans and not about walking. For that we have "збиратись (щось робити)": Are you going to go to the movies? - Ви збираєтесь йти в кіно?