code: func GetEtcdAltNames(cfg *kubeadmapi.InitConfiguration) (*certutil.AltNames, error) {
  	return getAltNames(cfg, kubeadmconstants.EtcdServerCertName)
  }
docs: // GetEtcdAltNames builds an AltNames object for generating the etcd server certificate.
  // `advertise address` and localhost are included in the SAN since this is the interfaces the etcd static pod listens on.
  // The user can override the listen address with `Etcd.ExtraArgs` and add SANs with `Etcd.ServerCertSANs`.