func GetOrRegisterGaugeFloat64(name string, r Registry) GaugeFloat64 {
	if nil == r {
		r = DefaultRegistry
	}
	return r.GetOrRegister(name, NewGaugeFloat64()).(GaugeFloat64)
}
GetOrRegisterGaugeFloat64 returns an existing GaugeFloat64 or constructs and registers a
new StandardGaugeFloat64.
package metrics
import (
	"math"
	"sync/atomic"
)
type GaugeFloat64 interface {
	Snapshot() GaugeFloat64
	Update(float64)
	Value() float64
}