type unionGauge … var _ … // NewUnionGauge constructs a Gauge that delegates to all of the given Gauges func NewUnionGauge(elts ...Gauge) Gauge { … } func (ug unionGauge) Set(x float64) { … } func (ug unionGauge) Add(x float64) { … } func (ug unionGauge) Inc() { … } func (ug unionGauge) Dec() { … } func (ug unionGauge) SetToCurrentTime() { … }