code: func (c *Controller) RenderFileName(filename string, delivery ContentDisposition) Result {
  	f, err := os.Open(filename)
  	if err != nil {
  		c.Log.Errorf("Cant open file: %v", err)
  		return c.RenderError(err)
  	}
  	return c.RenderFile(f, delivery)
  }
docs: // RenderFileName returns a file indicated by the path as provided via the filename.
  // It can be either displayed inline or downloaded as an attachment.
  // The name and size are taken from the file info.