code: func (hwm *HighWaterMark) Update(current int64) bool {
  	for {
  		old := atomic.LoadInt64((*int64)(hwm))
  		if current <= old {
  			return false
  		}
  		if atomic.CompareAndSwapInt64((*int64)(hwm), old, current) {
  			return true
  		}
  	}
  }
docs: // Update returns true if and only if 'current' is the highest value ever seen.