Selamlar server tarafı için yazdım kodumu paylaşayım ama js bilmiyorsanız bir işinize yaramaz sadece kodu kopyala yapıştır yapmak da yetmiyor zaten Ama yine de atayım belki fikir verir.

const { google } = require("googleapis");
const functions = require("firebase-functions");
const serviceAccount = require("./services_account.json");
const publisher = google.androidpublisher("v3");
const admin = require("firebase-admin");

let app = admin.initializeApp({
credential: admin.credential.cert(serviceAccount),
databaseURL: "https://xxxx-xxxx.firebaseio.com",
});

exports.userPreStatus = functions.https.onCall(async (req, res) => {
const purchaseToken = req.purchaseToken;
const subsId = req.subsId;
let client = new google.auth.JWT(
serviceAccount.client_email,
undefined,
serviceAccount.private_key,
["https://www.googleapis.com/auth/androidpublisher"]
);

const preResT = await publisher.purchases.subscriptions.get({
packageName: "com.xxxx.xxxx",
subscriptionId: subsId,
token: purchaseToken,
auth: client,
});

return preResT.data;
});

exports.userPreCancelStatus = functions.https.onCall(async (req, res) => {
const purchaseToken = req.purchaseToken;
const subsId = req.subsId;
let client = new google.auth.JWT(
serviceAccount.client_email,
undefined,
serviceAccount.private_key,
["https://www.googleapis.com/auth/androidpublisher"]
);

const preResT = await publisher.purchases.subscriptions.get({
packageName: "com.xxxx.xxxxx",
subscriptionId: subsId,
token: purchaseToken,
auth: client,
});

let resCanceled;
let dateCc = new Date();
if (Number(dateCc.getTime()) >= Number(preResT.data.expiryTimeMillis)) {
resCanceled = { canledSt: "canceled", canledStn: 1 };
} else {
resCanceled = { canledSt: "no", canledStn: 0 };
}

return resCanceled;
});