code: func DrawRectangles(img gocv.Mat, rects []image.Rectangle, r int, g int, b int, thickness int) {
  	for _, rect := range rects {
  		gocv.Rectangle(&img, rect, color.RGBA{uint8(r), uint8(g), uint8(b), 0}, thickness)
  	}
  	return
  }
docs: // DrawRectangles uses Rect array values to return image with rectangles drawn.