code: func NewRPCClient(cluster *Cluster, mvccStore MVCCStore) *RPCClient {
  	ch := make(chan *tikvrpc.Lease)
  	go tikvrpc.CheckStreamTimeoutLoop(ch)
  	return &RPCClient{
  		Cluster:       cluster,
  		MvccStore:     mvccStore,
  		streamTimeout: ch,
  	}
  }
docs: // NewRPCClient creates an RPCClient.
  // Note that close the RPCClient may close the underlying MvccStore.