One phrase, 2 meanings. Learn them one at a time, then test yourself.
Meaning 1 · most common
To suddenly become very angry, often showing it by shouting. Mainly British; in the US people say 'get mad'.
Example
A: Have you told Dad you scratched his car?
B: Not yet. He's going to go mad when he sees it.
Tell it apart
Meaning 2
To go mad means to become extremely upset, restless, or unable to cope with a situation.
Example
A: Why are you going for a walk in the rain?
B: I need some air or I will go mad.
Tell it apart
Read the sentence, then pick the meaning that's in play.
Pick a meaning and say it out loud. Save the ones you mix up.