code: func (d *FSDirectory) DeleteFile(name string) (err error) {
  	d.EnsureOpen()
  	if err = os.Remove(filepath.Join(d.path, name)); err == nil {
  		d.staleFilesLock.Lock()
  		defer d.staleFilesLock.Unlock()
  		delete(d.staleFiles, name)
  	}
  	return
  }
docs: // Removes an existing file in the directory.