code: func handlerName(h handlerFunc) string {
  	name := runtime.FuncForPC(reflect.ValueOf(h).Pointer()).Name()
  	parts := nameRegexp.FindStringSubmatch(name)
  	if len(parts) != 2 {
  		return ""
  	}
  	return parts[1]
  }
docs: // handlerName returns the name of the handler, which can be used as a metrics
  // postfix.