fix: create index failed without err (#285)

* fix: create index failed without err

* fix createIndex always return err

Author: zhangzhiqiangcs

migrator.go

@@ -146,7 +146,15 @@ func (m Migrator) CreateIndex(value interface{}, name string) error {
 					createIndexSQL += " WHERE " + idx.Where
 				}
 
-				return m.DB.Exec(createIndexSQL, values...).Error
+				err := m.DB.Exec(createIndexSQL, values...).Error
+				if err != nil {
+					return err
+				}
+
+				if !m.HasIndex(value, name) {
+					return fmt.Errorf("failed to create index with name %v", name)
+				}
+				return nil
 			}
 		}