code: func (enc *Encoder) Decode(id string) (uint64, error) {
  
  	if id == "" {
  		return 0, errors.New("base58: id should not be empty")
  	}
  
  	var n uint64
  	for i := range id {
  		u := enc.decodeMap[id[i]]
  		if u < 0 {
  			return 0, errors.New("base58: invalid character - " + string(id[i]))
  		}
  		n = n*58 + uint64(u)
  	}
  
  	return n, nil
  }
docs: // Decode returns decoded unsigned int64 by Base58.