code: func NewGaugeVec(opts prometheus.GaugeOpts, labelNames []string) *prometheus.GaugeVec {
  	g := prometheus.NewGaugeVec(opts, labelNames)
  	prometheus.MustRegister(g)
  	return g
  }
docs: // NewGaugeVec works like the function of the same name in the prometheus
  // package but it automatically registers the GaugeVec with the
  // prometheus.DefaultRegisterer. If the registration fails, NewGaugeVec panics.