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