code: func Dir(dir, prefix string) (string, io.Closer, error) {
  	// Create the temporary directory
  	td, err := ioutil.TempDir(dir, prefix)
  	if err != nil {
  		return "", nil, err
  	}
  
  	return filepath.Join(td, "temp"), pathCloser(td), nil
  }
docs: // Dir creates a new temporary directory that isn't yet created. This
  // can be used with calls that expect a non-existent directory.
  //
  // The directory is created as a child of a temporary directory created
  // within the directory dir starting with prefix. The temporary directory
  // returned is always named "temp". The parent directory has the specified
  // prefix.
  //
  // The returned io.Closer should be used to clean up the returned directory.
  // This will properly remove the returned directory and any other temporary
  // files created.
  //
  // If an error is returned, the Closer does not need to be called (and will
  // be nil).