code: func RequireAuth(h http.Handler, op Operation) http.Handler {
  	return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
  		if Allowed(req, op) {
  			h.ServeHTTP(rw, req)
  		} else {
  			SendUnauthorized(rw, req)
  		}
  	})
  }
docs: // RequireAuth wraps a function with another function that enforces
  // HTTP Basic Auth and checks if the operations in op are all permitted.