code: func (m *PathRecorderMux) UnlistedHandleFunc(path string, handler func(http.ResponseWriter, *http.Request)) {
  	m.UnlistedHandle(path, http.HandlerFunc(handler))
  }
docs: // UnlistedHandleFunc registers the handler function for the given pattern, but doesn't list it.
  // If a handler already exists for pattern, Handle panics.