logout method Null safety

Future<void> logout()

Invalidates current sesssion

Implementation

Future<void> logout() async {
  if (token == '') return;
  var res = await http
      .post(Uri.parse('https://api.mangadex.org/auth/logout'), headers: {
    HttpHeaders.authorizationHeader: 'Bearer $token',
    HttpHeaders.userAgentHeader: 'mangadex_dart_api/1.0'
  });
  var data = jsonDecode(res.body);
  if (res.statusCode == 403 && res.headers['X-Captcha-Sitekey'] != null) {
    throw CaptchaException(res.headers['X-Captcha-Sitekey'].toString(),
        message:
            'You need to solve a captcha, check `.sitekey` for the sitekey.');
  }
  if (res.statusCode != 200) {
    throw 'An error has happened: ${data["errors"][0]["title"]} - ${data["errors"][0]["detail"]}';
  }
  token = '';
  refresh = '';
}