code: func incByteSlice(b []byte) (next []byte) {
  	l := len(b)
  	next = make([]byte, l)
  	copy(next, b)
  	for i := l - 1; i >= 0; i-- {
  		if b[i] == 255 {
  			next[i] = 0
  		} else {
  			next[i] = b[i] + 1
  			return next
  		}
  	}
  	return nil
  }
docs: // incByteSlice returns the byte slice of the same size
  // of the provided one that is by one incremented in its
  // total value. If all bytes in provided slice are equal
  // to 255 a nil slice would be returned indicating that
  // increment can not happen for the same length.