Modernize code with go fix

internal/mysql/node.go

@@ -510,15 +510,15 @@ func (n *Node) GetDiskUsage() (used uint64, total uint64, err error) {
 }
 
 func getFlagsFromProcMounts(file, filesystem string) (string, error) {
-	for _, line := range strings.Split(file, "\n") {
+	for line := range strings.SplitSeq(file, "\n") {
 		components := strings.Split(line, " ")
 		if len(components) < 3 {
 			continue
 		}
 
 		if components[1] == filesystem {
-			flags := strings.Split(components[3], ",")
-			for _, flag := range flags {
+			flags := strings.SplitSeq(components[3], ",")
+			for flag := range flags {
 				if flag == "ro" || flag == "rw" {
 					return flag, nil
 				}

tests/mysync_test.go

@@ -139,11 +139,11 @@ func (tctx *testContext) saveLogs(scenario string) error {
 		}
 	}
 	if len(errs) > 0 {
-		msg := ""
+		var msg strings.Builder
 		for _, err := range errs {
-			msg += err.Error() + "\n"
+			msg.WriteString(err.Error() + "\n")
 		}
-		return errors.New(msg)
+		return errors.New(msg.String())
 	}
 	return nil
 }