code: func Hash(key uint64, numBuckets int) int32 {
  
  	var b int64 = -1
  	var j int64
  
  	for j < int64(numBuckets) {
  		b = j
  		key = key*2862933555777941757 + 1
  		j = int64(float64(b+1) * (float64(int64(1)<<31) / float64((key>>33)+1)))
  	}
  
  	return int32(b)
  }
docs: // Hash consistently chooses a hash bucket number in the range [0, numBuckets) for the given key. numBuckets must be >= 1.