code: func (j *joinData) ClientSet() (*clientset.Clientset, error) {
  	if j.clientSet != nil {
  		return j.clientSet, nil
  	}
  	path := kubeadmconstants.GetAdminKubeConfigPath()
  	client, err := kubeconfigutil.ClientSetFromFile(path)
  	if err != nil {
  		return nil, errors.Wrap(err, "[preflight] couldn't create Kubernetes client")
  	}
  	j.clientSet = client
  	return client, nil
  }
docs: // ClientSet returns the ClientSet for accessing the cluster with the identity defined in admin.conf.