code: func Encode(value uint64) string {
  	var res [16]byte
  	var i int
  	for i = len(res) - 1; value != 0; i-- {
  		res[i] = base36[value%36]
  		value /= 36
  	}
  	return string(res[i+1:])
  }
docs: // Encode encodes a number to base36.