1 If the sun goes in, it becomes hidden from view by clouds. -- (太阳)被云遮住
2 If a fact or piece of information goes in, you understand it or remember it. -- 被理解,被领会;被记住
It's getting cold. Shall we go in?
The students looked nervous as they were going in for the exam.
I like the look of that hairdresser's. I'm going to go in and make an appointment.