code: func (g *Group) setEvaluationDuration(dur time.Duration) {
  	g.metrics.groupLastDuration.WithLabelValues(groupKey(g.file, g.name)).Set(dur.Seconds())
  
  	g.mtx.Lock()
  	defer g.mtx.Unlock()
  	g.evaluationDuration = dur
  }
docs: // setEvaluationDuration sets the time in seconds the last evaluation took.