session add method IsInTx

add session IsInTx

session_tx.go

@@ -84,3 +84,8 @@ func (session *Session) Commit() error {
 	}
 	return nil
 }
+
+// if current session is in a transaction
+func (session *Session) IsInTx() bool {
+	return !session.isAutoCommit
+}