code: func fetchInitConfigurationFromJoinConfiguration(cfg *kubeadmapi.JoinConfiguration, tlsBootstrapCfg *clientcmdapi.Config) (*kubeadmapi.InitConfiguration, error) {
  	// Retrieves the kubeadm configuration
  	klog.V(1).Infoln("[preflight] Retrieving KubeConfig objects")
  	initConfiguration, err := fetchInitConfiguration(tlsBootstrapCfg)
  	if err != nil {
  		return nil, err
  	}
  
  	// Create the final KubeConfig file with the cluster name discovered after fetching the cluster configuration
  	clusterinfo := kubeconfigutil.GetClusterFromKubeConfig(tlsBootstrapCfg)
  	tlsBootstrapCfg.Clusters = map[string]*clientcmdapi.Cluster{
  		initConfiguration.ClusterName: clusterinfo,
  	}
  	tlsBootstrapCfg.Contexts[tlsBootstrapCfg.CurrentContext].Cluster = initConfiguration.ClusterName
  
  	// injects into the kubeadm configuration the information about the joining node
  	initConfiguration.NodeRegistration = cfg.NodeRegistration
  	if cfg.ControlPlane != nil {
  		initConfiguration.LocalAPIEndpoint = cfg.ControlPlane.LocalAPIEndpoint
  	}
  
  	return initConfiguration, nil
  }
docs: // fetchInitConfigurationFromJoinConfiguration retrieves the init configuration from a join configuration, performing the discovery