code: func (rd *RAMDirectory) DeleteFile(name string) error {
  	rd.EnsureOpen()
  	rd.fileMapLock.RLock()
  	defer rd.fileMapLock.RUnlock()
  	if file, ok := rd.fileMap[name]; ok {
  		file.directory = nil
  		atomic.AddInt64(&rd.sizeInBytes, -file.sizeInBytes)
  		return nil
  	}
  	return errors.New(name)
  }
docs: /* Removes an existing file in the directory */