Closing a channel conceptually works by sending a special “close token” over this channel. You close a channel when you have a finite sequence of elements to be processed by consumers and you must signal to the consumers that this sequence is over. You don’t have to close a channel otherwise.
Channels are not tied to any native resource and they don’t have to be closed to release their memory. Simply dropping all the references to a channel is fine. GC will come to do clean it up.