add other session providers (#5963)

vendor/github.com/lunny/nodb/store/goleveldb/snapshot.go

@@ -0,0 +1,26 @@
+package goleveldb
+
+import (
+	"github.com/lunny/nodb/store/driver"
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+type Snapshot struct {
+	db  *DB
+	snp *leveldb.Snapshot
+}
+
+func (s *Snapshot) Get(key []byte) ([]byte, error) {
+	return s.snp.Get(key, s.db.iteratorOpts)
+}
+
+func (s *Snapshot) NewIterator() driver.IIterator {
+	it := &Iterator{
+		s.snp.NewIterator(nil, s.db.iteratorOpts),
+	}
+	return it
+}
+
+func (s *Snapshot) Close() {
+	s.snp.Release()
+}