code: func (w *EtcdSafePointKV) Put(k string, v string) error {
  	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
  	_, err := w.cli.Put(ctx, k, v)
  	cancel()
  	if err != nil {
  		return errors.Trace(err)
  	}
  	return nil
  }
docs: // Put implements the Put method for SafePointKV