code: func findProtoFiles(dir string) ([]string, error) {
  	files, err := filepath.Glob(filepath.Join(dir, "*.proto"))
  	if err != nil {
  		return nil, err
  	}
  
  	for i, f := range files {
  		files[i] = filepath.Base(f)
  	}
  	return files, err
  }
docs: // findProtoFiles returns .proto files in dir. The returned file paths
  // are relative to dir.