code: func (f *Factory) Timer(options metrics.TimerOptions) metrics.Timer {
  	timer := &timer{
  		timers: make([]metrics.Timer, len(f.factories)),
  	}
  	for i, factory := range f.factories {
  		timer.timers[i] = factory.Timer(options)
  	}
  	return timer
  }
docs: // Timer implements metrics.Factory interface