code: func (c *Controller) RenderBinary(memfile io.Reader, filename string, delivery ContentDisposition, modtime time.Time) Result {
  	c.setStatusIfNil(http.StatusOK)
  
  	return &BinaryResult{
  		Reader:   memfile,
  		Name:     filename,
  		Delivery: delivery,
  		Length:   -1, // http.ServeContent gets the length itself unless memfile is a stream.
  		ModTime:  modtime,
  	}
  }
docs: // RenderBinary is like RenderFile() except that it instead of a file on disk,
  // it renders data from memory (which could be a file that has not been written,
  // the output from some function, or bytes streamed from somewhere else, as long
  // it implements io.Reader).  When called directly on something generated or
  // streamed, modtime should mostly likely be time.Now().