fix(export-backup): fix memory leak in backup export (#7452)

There was a memory leak because the program exits before DB close.

(cherry picked from commit 2eb7bc8)

Author: NamanJain8

worker/file_handler.go

@@ -366,7 +366,6 @@ func (h *fileHandler) ExportBackup(backupDir, exportDir, format string,
 				ch <- errors.Wrapf(err, "cannot open DB at %s", dir)
 				return
 			}
-			defer db.Close()
 
 			req := &pb.ExportRequest{
 				GroupId:     group,
@@ -377,6 +376,9 @@ func (h *fileHandler) ExportBackup(backupDir, exportDir, format string,
 			}
 
 			_, err = exportInternal(context.Background(), req, db, true)
+			// It is important to close the db before sending err to ch. Else, we will see a memory
+			// leak.
+			db.Close()
 			ch <- errors.Wrapf(err, "cannot export data inside DB at %s", dir)
 		}(gid)
 	}