code: func Encode(dst, src []byte) int {
  	for i, v := range src {
  		dst[i*2] = hextable[v>>4]
  		dst[i*2+1] = hextable[v&0x0f]
  	}
  
  	return len(src) * 2
  }
docs: // Encode encodes src into EncodedLen(len(src))
  // bytes of dst. As a convenience, it returns the number
  // of bytes written to dst, but this value is always EncodedLen(len(src)).
  // Encode implements hexadecimal encoding.