clientv3/namespace/kv.go
func NewKV(kv clientv3.KV, prefix string) clientv3.KV {
	return &kvPrefix{kv, prefix}
}
func NewKV(kv clientv3.KV, prefix string) clientv3.KV {
	return &kvPrefix{kv, prefix}
}
// NewKV wraps a KV instance so that all requests
// are prefixed with a given string.