There is no difference in meaning. In each case, one form of the sentence uses the gerund form of the verb (going or coming) which turns it into a noun. This requires the insertion of an auxilliary verb, in your sentences "be", to complete the action of the sentence. The combination of the auxilliary verb and the gerund becomes the present participle form. That was probably a lot of explanation just to say there is no difference!!

i'm coming and i'll come,哪有什么区别，should 改成shall也没事,这是基本的语法，不用多想了