code: func (s SourceFilesystems) StatResource(lang, filename string) (fi os.FileInfo, fs afero.Fs, err error) {
  	for _, fsToCheck := range []afero.Fs{s.StaticFs(lang), s.Assets.Fs, s.Content.Fs} {
  		fs = fsToCheck
  		fi, err = fs.Stat(filename)
  		if err == nil || !os.IsNotExist(err) {
  			return
  		}
  	}
  	// Not found.
  	return
  }
docs: // StatResource looks for a resource in these filesystems in order: static, assets and finally content.
  // If found in any of them, it returns FileInfo and the relevant filesystem.
  // Any non os.IsNotExist error will be returned.
  // An os.IsNotExist error wil be returned only if all filesystems return such an error.
  // Note that if we only wanted to find the file, we could create a composite Afero fs,
  // but we also need to know which filesystem root it lives in.