code: func (j *joinData) TLSBootstrapCfg() (*clientcmdapi.Config, error) {
  	if j.tlsBootstrapCfg != nil {
  		return j.tlsBootstrapCfg, nil
  	}
  	klog.V(1).Infoln("[preflight] Discovering cluster-info")
  	tlsBootstrapCfg, err := discovery.For(j.cfg)
  	j.tlsBootstrapCfg = tlsBootstrapCfg
  	return tlsBootstrapCfg, err
  }
docs: // TLSBootstrapCfg returns the cluster-info (kubeconfig).