What happened:
The testTemplate function creates a temp config(os.CreateTemp(tmpDir, tempNginxPattern)) in the tempDir/nginx directory (tmpDir := os.TempDir() + "/nginx") but the cleanTempNginxCfg function cleans only the tmp directory. This means that this function does not work, and wrong nginx temp configs are not deleted, and it leads to clogging up FS. And there is a wrong test, because the test creates files in the temp dir, and that is why it passes now.

Mistake is this function:

	err := filepath.Walk(os.TempDir(), func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() && os.TempDir() != path {
			return filepath.SkipDir
		}

		dur, err := time.ParseDuration("-5m")
		if err != nil {
			return err
		}
		fiveMinutesAgo := time.Now().Add(dur)
		if strings.HasPrefix(info.Name(), tempNginxPattern) && info.ModTime().Before(fiveMinutesAgo) {
			files = append(files, path)
		}
		return nil
	})

Due to this condition the function checks only the temp dir and does not check nested tempDir/nginx

if info.IsDir() && os.TempDir() != path {
   return filepath.SkipDir
}

What you expected to happen:
Wrong nginx temp configs are deleted.

How to reproduce this issue:
Create nginx temp configs(files whose name begins with prefix nginx-cfg) in tempDir/nginx and wait 6 minutes, nothing will happen.