fluwx/doc/PAYMENT.md

Payment

Calling payment is easy but to make it work isn't not so easy:

fluwx.pay(
      which: Payment(
      appId: result['appid'].toString(),
      partnerId: result['partnerid'].toString(),
      prepayId: result['prepayid'].toString(),
      packageValue: result['package'].toString(),
      nonceStr: result['noncestr'].toString(),
      timestamp: result['timestamp'],
      sign: result['sign'].toString(),
));

Take a look at payment document for help.