etcdserver/api/v2discovery/discovery.go
func JoinCluster(lg *zap.Logger, durl, dproxyurl string, id types.ID, config string) (string, error) {
	d, err := newDiscovery(lg, durl, dproxyurl, id)
	if err != nil {
		return "", err
	}
	return d.joinCluster(config)
}
func JoinCluster(lg *zap.Logger, durl, dproxyurl string, id types.ID, config string) (string, error) {
	d, err := newDiscovery(lg, durl, dproxyurl, id)
	if err != nil {
		return "", err
	}
	return d.joinCluster(config)
}
// JoinCluster will connect to the discovery service at the given url, and
// register the server represented by the given id and config to the cluster