code: func RandFontFamily() (*truetype.Font, error) {
  	fontFile := fontFamily[r.Intn(len(fontFamily))]
  
  	fontBytes, err := ioutil.ReadFile(fontFile)
  	if err != nil {
  		log.Println(err)
  		return &truetype.Font{}, err
  	}
  	f, err := freetype.ParseFont(fontBytes)
  	if err != nil {
  		log.Println(err)
  		return &truetype.Font{}, err
  	}
  	return f, nil
  }
docs: //获取所及字体.