defer unLocker()
			}
			gatherers = append(gatherers, gatherer)
		}
	}

	if len(gatherers) == 0 {
		return notFoundHandler
	}

	return promhttp.HandlerFor(prometheus.Gatherers(gatherers), h.opts)
}

// ServeHTTP - implements http.Handler interface.
//
// When the `list` query parameter is provided (its value is ignored), the