datastore/query.go
func callNext(c context.Context, res *pb.QueryResult, offset, count int32) error {
	if res.Cursor == nil {
		return errors.New("datastore: internal error: server did not return a cursor")
	}
	req := &pb.NextRequest{
		Cursor: res.Cursor,
	}
	if count >= 0 {
		req.Count = proto.Int32(count)
	}
	if offset != 0 {
		req.Offset = proto.Int32(offset)
	}
	if res.CompiledCursor != nil {
		req.Compile = proto.Bool(true)
	}
	res.Reset()
	return internal.Call(c, "datastore_v3", "Next", req, res)
}
func callNext(c context.Context, res *pb.QueryResult, offset, count int32) error {
	if res.Cursor == nil {
		return errors.New("datastore: internal error: server did not return a cursor")
	}
	req := &pb.NextRequest{
		Cursor: res.Cursor,
	}
	if count >= 0 {
		req.Count = proto.Int32(count)
	}
	if offset != 0 {
		req.Offset = proto.Int32(offset)
	}
	if res.CompiledCursor != nil {
		req.Compile = proto.Bool(true)
	}
	res.Reset()
	return internal.Call(c, "datastore_v3", "Next", req, res)
}
// callNext issues a datastore_v3/Next RPC to advance a cursor, such as that
// returned by a query with more results.