Well over half of the code I've ever seen that uses three or more channels (i.e. two semantic ones plus a cancellation or shutdown) has had serious flaws in it.

Granted, that generally means they're doing something non-trivial with concurrency, and that correlates strongly with "has concurrency bugs". But I see issues FAR more frequently when they reach for channels rather than mutexes. It's bad enough that I just check absolutely every three-chan chunk of code proactively now.

I lay part of the blame on Go's "♥ safe and easy concurrency with channels! ♥" messaging. And another large chunk at the lack of generics (until recently), making abstracting these kinds of things extremely painful. Combined, you get "just do it by hand lol, it's easy / get good" programming, which is always a source of "fun".