gototp.go
func (totp *TOTP) QRCodeGoogleChartsUrl(label string, width int) string {
	return fmt.Sprintf("https://chart.googleapis.com/chart?cht=qr&chs=%vx%v&chl=%v", width, width, url.QueryEscape(totp.QRCodeData(label)))
}
func (totp *TOTP) QRCodeGoogleChartsUrl(label string, width int) string {
	return fmt.Sprintf("https://chart.googleapis.com/chart?cht=qr&chs=%vx%v&chl=%v", width, width, url.QueryEscape(totp.QRCodeData(label)))
}
// Return a URL to generate a QRCode on Google Charts for the TOTP, with the given 
// label and width (and height equal to width).