There are even better muxes now. `pressly/chi` is used by heavy hitters in production and takes advantage of Go 1.7 HTTP context. `labstack/echo` is another highly recommended by others but I don't like the non-idiomatic echo.Context in handler signatures.
Back on topic, I hope the go web examples only imports built-in packages. The gorilla/mux example could easily be written to use built-in packages.