code: func HashString(key string, buckets int32, h KeyHasher) int32 {
  	h.Reset()
  	_, err := io.WriteString(h, key)
  	if err != nil {
  		panic(err)
  	}
  	return Hash(h.Sum64(), buckets)
  }
docs: // HashString takes string as key instead of an int and uses a KeyHasher to
  // generate a key compatible with Hash().