code: func (c *Controller) RenderFile(file *os.File, delivery ContentDisposition) Result {
  	c.setStatusIfNil(http.StatusOK)
  
  	var (
  		modtime       = time.Now()
  		fileInfo, err = file.Stat()
  	)
  	if err != nil {
  		controllerLog.Error("RenderFile: error", "error", err)
  	}
  	if fileInfo != nil {
  		modtime = fileInfo.ModTime()
  	}
  	return c.RenderBinary(file, filepath.Base(file.Name()), delivery, modtime)
  }
docs: // RenderFile returns a file, either displayed inline or downloaded
  // as an attachment. The name and size are taken from the file info.