code: func (b *Base64) UnmarshalText(data []byte) error { // validation is performed later on
  	enc := base64.URLEncoding
  	dbuf := make([]byte, enc.DecodedLen(len(data)))
  
  	n, err := enc.Decode(dbuf, data)
  	if err != nil {
  		return err
  	}
  
  	*b = dbuf[:n]
  	return nil
  }
docs: // UnmarshalText hydrates this instance from text