package chronoimport ("time")// Meter is a simple stopwatchtype Meter struct {elapsed time.Durationmark *time.Time}func (m *Meter) Start() {m.mark = new(time.Now())}func (m *Meter) Stop() time.Duration {if m.mark == nil {return m.elapsed}m.elapsed += time.Since(*m.mark)m.mark = nilreturn m.elapsed}func (m *Meter) Elapsed() time.Duration {elapsed := m.elapsedif m.mark != nil {elapsed += time.Since(*m.mark)}return elapsed}