How to work with concurrent access to one memory cell?

Question

go

Small chat (for self-study) on GO. The "server" package has "map[string]net.Conn" where all active channels are stored.
I delete the empty channel from memory as soon as the last user exits.
During testing, I noticed that there are 2 different streams .. one is trying to delete an empty channel and the second is trying to write a new connection there.
It's not clear how to work with this.

Answer 1

Use mutexes when running concurrently with map
https://gobyexample.com/mutexes

Answer 2

Mutexes
A visual graph with the code https://golangbot.com/mutex/
+ it is mandatory for readers and writers to use RLock and RUnlock (lock on reading the value or on writing)
very useful