Assuming you've got a buffered channel with non-blocking send and receive calls, I seriously doubt that the three lines protected by a mutex are the bottleneck

Assuming you've got a buffered channel with non-blocking send and receive calls, I seriously doubt that the three lines protected by a mutex are the bottleneck for scaling your service. It's basically exchanging one set of atomic ops for another one. I'm not saying that you couldn't optimize if you have a very specific need, but it's disingenuous to pretend that the lack of a "lock-free" queue is somehow a fatal flaw or preventing you from scaling go programs.