func (m *Member) WriteHealthKey() error {
	cli, err := m.CreateEtcdClient()
	if err != nil {
		return fmt.Errorf("%v (%q)", err, m.EtcdClientEndpoint)
	}
	defer cli.Close()

	// give enough time-out in case expensive requests (range/delete) are pending
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	_, err = cli.Put(ctx, "health", "good")
	cancel()
	if err != nil {
		return fmt.Errorf("%v (%q)", err, m.EtcdClientEndpoint)
	}
	return nil
}
func (m *Member) WriteHealthKey() error {
	cli, err := m.CreateEtcdClient()
	if err != nil {
		return fmt.Errorf("%v (%q)", err, m.EtcdClientEndpoint)
	}
	defer cli.Close()

	// give enough time-out in case expensive requests (range/delete) are pending
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	_, err = cli.Put(ctx, "health", "good")
	cancel()
	if err != nil {
		return fmt.Errorf("%v (%q)", err, m.EtcdClientEndpoint)
	}
	return nil
}
// WriteHealthKey writes a health key to this member.