Sqlite backend: Unlock the mutex in Allkeys correctly.

sqlite.go

@@ -216,24 +216,27 @@ func (ss *SqliteSession) CommitTransaction() error {
 }
 
 func (ss *SqliteSession) AllKeys(hash []byte) (keys chan []byte, n int, err error) {
-	globalLock.Lock()
-	defer globalLock.Unlock()
+	globalLock.RLock()
 
 	countStmt := ss.txStmt(ss.backend.countStmt)
 	if err = countStmt.QueryRow().Scan(&n); err != nil {
 		if err == sql.ErrNoRows {
 			err = nil
 		}
+		globalLock.RUnlock()
 		return
 	}
 
 	keysStmt := ss.txStmt(ss.backend.keysStmt)
 	var rows *sql.Rows
 	if rows, err = keysStmt.Query(); err != nil {
+		globalLock.RUnlock()
 		return
 	}
+
 	keys = make(chan []byte)
 	go func() {
+		defer globalLock.RUnlock()
 		defer rows.Close()
 		defer close(keys)
 		for rows.Next() {