code: func (c Crawler) GetContentType(document *goquery.Document) string {
  	var attr string
  	// <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  	document.Find("meta[http-equiv#=(?i)^Content\\-type$]").Each(func(i int, s *goquery.Selection) {
  		attr, _ = s.Attr("content")
  	})
  	return attr
  }
docs: // GetContentType returns the Content-Type string extracted from the meta tags