clientv3/op.go
func withTop(target SortTarget, order SortOrder) []OpOption {
	return []OpOption{WithPrefix(), WithSort(target, order), WithLimit(1)}
}
func withTop(target SortTarget, order SortOrder) []OpOption {
	return []OpOption{WithPrefix(), WithSort(target, order), WithLimit(1)}
}
// withTop gets the first key over the get's prefix given a sort order