Fix concurrent access on task returnError

Author: nekohasekai

common/task/task.go

@@ -87,16 +87,18 @@ func (g *Group) RunContextList(contextList []context.Context) error {
 	}
 
 	selectedContext, upstreamErr := common.SelectContext(append([]context.Context{taskCancelContext}, contextList...))
-	if selectedContext != 0 {
-		returnError = E.Append(returnError, upstreamErr, func(err error) error {
-			return E.Cause(err, "upstream")
-		})
-	}
 
 	if g.cleanup != nil {
 		g.cleanup()
 	}
 
 	<-taskContext.Done()
+
+	if selectedContext != 0 {
+		returnError = E.Append(returnError, upstreamErr, func(err error) error {
+			return E.Cause(err, "upstream")
+		})
+	}
+
 	return returnError
 }