code: func (a *awareness) ApplyDelta(delta int) {
  	a.Lock()
  	initial := a.score
  	a.score += delta
  	if a.score < 0 {
  		a.score = 0
  	} else if a.score > (a.max - 1) {
  		a.score = (a.max - 1)
  	}
  	final := a.score
  	a.Unlock()
  
  	if initial != final {
  		metrics.SetGauge([]string{"memberlist", "health", "score"}, float32(final))
  	}
  }
docs: // ApplyDelta takes the given delta and applies it to the score in a thread-safe
  // manner. It also enforces a floor of zero and a max of max, so deltas may not
  // change the overall score if it's railed at one of the extremes.