I would like to know what the difference between "come in" and "go in" is. Let's say a little boy, a student, is standing outside the class room and the teacher is in. Then the student say:
- Teacher may I come in.
Why didn't the student just say "Teacher may I go in"?
Also, if the teacher and the student are standing outside the class room, how should the student say to the teacher?
- Teacher, may I come in?
- Teacher, may I go in?