code: func (m *Mercury) BatchCreate(ctx context.Context, data map[string]string, opts ...clientv3.OpOption) (*clientv3.TxnResponse, error) {
  	limit := map[string]map[int]string{}
  	for key := range data {
  		limit[key] = map[int]string{0: "="}
  	}
  	resp, err := m.batchPut(ctx, data, limit, opts...)
  	if err != nil {
  		return resp, err
  	}
  	if !resp.Succeeded {
  		return resp, types.ErrKeyExists
  	}
  	return resp, nil
  }
docs: // BatchCreate create key values if not exists