Implement Key/Value on Iterator for GoLevelDB

This is needed because leveldb reuses the keys on each iteration.
In our wrapper, we copy the key/value so that it is safe to store.

db/go_level_db.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	"github.com/syndtr/goleveldb/leveldb/util"
 
@@ -116,12 +117,32 @@ func (db *GoLevelDB) Stats() map[string]string {
 	return stats
 }
 
+type goLevelDBIterator struct {
+	iterator.Iterator
+}
+
+func (it *goLevelDBIterator) Key() []byte {
+	key := it.Key()
+	k := make([]byte, len(key))
+	copy(k, key)
+
+	return k
+}
+
+func (it *goLevelDBIterator) Value() []byte {
+	val := it.Value()
+	v := make([]byte, len(val))
+	copy(v, val)
+
+	return v
+}
+
 func (db *GoLevelDB) Iterator() Iterator {
-	return db.db.NewIterator(nil, nil)
+	return &goLevelDBIterator{db.db.NewIterator(nil, nil)}
 }
 
 func (db *GoLevelDB) IteratorPrefix(prefix []byte) Iterator {
-	return db.db.NewIterator(util.BytesPrefix(prefix), nil)
+	return &goLevelDBIterator{db.db.NewIterator(util.BytesPrefix(prefix), nil)}
 }
 
 func (db *GoLevelDB) NewBatch() Batch {