code: func ClientTLSConfig(cl *http.Client) *tls.Config {
  	if cl.Transport == nil {
  		cl.Transport = http.DefaultTransport
  	}
  	tr := cl.Transport.(*http.Transport)
  	if tr.TLSClientConfig == nil {
  		tr.TLSClientConfig = &tls.Config{}
  	}
  	return tr.TLSClientConfig
  }
docs: // Returns the http.Client's TLS Config, traversing and generating any
  // defaults along the way to get it.