code: func (s *ProviderServer) CleanUp(domain, token, keyAuth string) error {
  	if s.listener == nil {
  		return nil
  	}
  
  	// Server was created, close it.
  	if err := s.listener.Close(); err != nil && err != http.ErrServerClosed {
  		return err
  	}
  
  	return nil
  }
docs: // CleanUp closes the HTTPS server.