code: func EnsureDNSAddon(cfg *kubeadmapi.ClusterConfiguration, client clientset.Interface) error {
  	if cfg.DNS.Type == kubeadmapi.CoreDNS {
  		return coreDNSAddon(cfg, client)
  	}
  	return kubeDNSAddon(cfg, client)
  }
docs: // EnsureDNSAddon creates the kube-dns or CoreDNS addon