code: func (c *Context) DataFromReader(code int, contentLength int64, contentType string, reader io.Reader, extraHeaders map[string]string) {
  	c.Render(code, render.Reader{
  		Headers:       extraHeaders,
  		ContentType:   contentType,
  		ContentLength: contentLength,
  		Reader:        reader,
  	})
  }
docs: // DataFromReader writes the specified reader into the body stream and updates the HTTP code.