if we want to add an endpoint with lease, we need this option.
for example:
resp, err := cli.Grant(context.TODO(), 5)
if err != nil {
log.Fatal(err)
}
err = r.Update(context.TODO(), serviceName, naming.Update{Op:naming.Add, Addr: exposedAddr}, clientv3.WithLease(resp.ID))
if err != nil {
log.Fatalf(err)
}
Previous implementation watches a single key so there's no way
to have separate hosts associate with separate keys for a single
grpc target. Instead, accept all keys on a prefix.
Also fixes first the Next() to read current name data from etcd instead
of waiting for the next event on a synced watcher.
Gyu-Ho Lee