code: func NewDNSProviderConfig(config *Config) (*DNSProvider, error) {
  	if config == nil {
  		return nil, errors.New("inwx: the configuration of the DNS provider is nil")
  	}
  
  	if config.Username == "" || config.Password == "" {
  		return nil, fmt.Errorf("inwx: credentials missing")
  	}
  
  	if config.Sandbox {
  		log.Infof("inwx: sandbox mode is enabled")
  	}
  
  	client := goinwx.NewClient(config.Username, config.Password, &goinwx.ClientOptions{Sandbox: config.Sandbox})
  
  	return &DNSProvider{config: config, client: client}, nil
  }
docs: // NewDNSProviderConfig return a DNSProvider instance configured for Dyn DNS