I get "chan chan"s pretty routinely. It is when I send a message to some internal server/actor, and I also send it the channel to reply on in the message. Usually it ends up being a "chan struct { ... something with a chan in it ... }" rather than a literal "chan chan" you can grep for, but the principle is there. Very useful pattern; I consider it one of the basics in Go.

"chan chan chan" never, as far as I know.

It would be overkill to replace everything like that with a message bus. Very different performance characteristics for one thing. Go's channels are very much an internal-to-the-OS-process construct, if I'm talking internal to the OS process there's no value in "upgrading" to a message bus.