code: func getInputFiles(inputDir string) (res []string, err error) {
  	files, err := ioutil.ReadDir(inputDir)
  	if err != nil {
  		return nil, fmt.Errorf("reading directory %s failed: %v", inputDir, err)
  	}
  	for _, f := range files {
  		if strings.HasSuffix(f.Name(), inputFileExt) {
  			res = append(res, filepath.Join(inputDir, f.Name()))
  		}
  	}
  	return res, nil
  }
docs: // getInputFiles returns all input files located in specified directory