It's a common grammatical construction used to form a command or request.
For example:
* "Go be quiet."
* "Go be a good boy."
* "Go be happy."
Idioms are phrases where the meaning is not literal and cannot be understood by analyzing the individual words.
Some examples of idioms include:
* "Kick the bucket" (to die)
* "Spill the beans" (to reveal a secret)
* "Break a leg" (good luck)
Let me know if you have any other phrases you'd like to check!