code: func OpenFileForWriting(fs afero.Fs, filename string) (afero.File, error) {
  	filename = filepath.Clean(filename)
  	// Create will truncate if file already exists.
  	// os.Create will create any new files with mode 0666 (before umask).
  	f, err := fs.Create(filename)
  	if err != nil {
  		if !os.IsNotExist(err) {
  			return nil, err
  		}
  		if err = fs.MkdirAll(filepath.Dir(filename), 0777); err != nil { //  before umask
  			return nil, err
  		}
  		f, err = fs.Create(filename)
  	}
  
  	return f, err
  }
docs: // OpenFileForWriting opens or creates the given file. If the target directory
  // does not exist, it gets created.