code: func (ix *IndexWriter) AddFile(name string) {
  	f, err := os.Open(name)
  	if err != nil {
  		log.Print(err)
  		return
  	}
  	defer f.Close()
  	ix.Add(name, f)
  }
docs: // AddFile adds the file with the given name (opened using os.Open)
  // to the index.  It logs errors using package log.