instruments.go
func (g *Gauge) Update(v float64) {
	atomic.StoreUint64(&g.value, math.Float64bits(v))
}
func (g *Gauge) Update(v float64) {
	atomic.StoreUint64(&g.value, math.Float64bits(v))
}
func ( g * Gauge ) Update ( v float64 ) { atomic . StoreUint64 ( & g . value , math . Float64bits ( v ) ) }
// Update updates the current stored value.
Update updates the current stored value .