code: func (store *FileStore) all() []string {
  	var err error
  	var keys []string
  	var files fileInfos
  
  	if !store.opened {
  		ERROR.Println(STR, "Trying to use file store, but not open")
  		return nil
  	}
  
  	files, err = ioutil.ReadDir(store.directory)
  	chkerr(err)
  	sort.Sort(files)
  	for _, f := range files {
  		DEBUG.Println(STR, "file in All():", f.Name())
  		name := f.Name()
  		if name[len(name)-4:len(name)] != msgExt {
  			DEBUG.Println(STR, "skipping file, doesn't have right extension: ", name)
  			continue
  		}
  		key := name[0 : len(name)-4] // remove file extension
  		keys = append(keys, key)
  	}
  	return keys
  }
docs: // lockless