instruments.go
func (r *Reservoir) Snapshot() Distribution {
	h := newHistogram(defaultHistogramSize)
	r.m.Lock()
	h = r.hist.Copy(h)
	r.m.Unlock()
	return h
}
func (r *Reservoir) Snapshot() Distribution {
	h := newHistogram(defaultHistogramSize)
	r.m.Lock()
	h = r.hist.Copy(h)
	r.m.Unlock()
	return h
}
func ( r * Reservoir ) Snapshot ( ) Distribution { h := newHistogram ( defaultHistogramSize ) r . m . Lock ( ) h = r . hist . Copy ( h ) r . m . Unlock ( ) return h }
// Snapshot returns a Distribution
Snapshot returns a Distribution