code: func (h *mutFileHandle) Release(ctx context.Context, req *fuse.ReleaseRequest) error {
  	h.tmp.Close()
  	os.Remove(h.tmp.Name())
  	h.tmp = nil
  
  	return nil
  }
docs: // Release is called when a file handle is no longer needed.  This is
  // called asynchronously after the last handle to a file is closed.