code: func (cfg *Config) Validate() error {
  	i, err := strconv.Atoi(cfg.Port)
  	if err != nil {
  		return ErrInvalidPort
  	}
  
  	if i <= 0 || i > 65535 {
  		return ErrInvalidPort
  	}
  
  	return nil
  }
docs: // Validate the config parsed into the Config struct