I don't usually say this but - isn't this a poor choice of name? Gorilla framework's Mux [0] has been around awhile and is quite popular for routing in Go.
Historically gophers haven't minded the occasional namespace collision: https://github.com/golang/go/issues/9
If it was "github.com/foo/poppycock" I could just write import mux "github.com/foo/poppycock" and use it as mux.
Import name similarity is a terrible argument for picking a name.