func (t Timer) Done() {
	t.done(t.start, t.metric)
}
Done end time measurement
package monitoring
import "time"
type Reporter interface {
	Counter(label string, val float64)
	Inc(label string)
	Histogram(label string, val float64)
	Gauge(label string, val float64)
	Timer(label string) Timer
}
type Timer struct {
	start  time.Time
	metric string
	done   func(start time.Time, metric string)
}