Update app.js

app.js

@@ -10,7 +10,12 @@ import admin from 'firebase-admin';
 // If you do not have 'serviceAccountKey.json', this will gracefully degrade to memory-only
 let db = null;
 try {
-    if (fs.existsSync('./serviceAccountKey.json')) {
+// The env secret MUST contain the full JSON string
+// exactly like the serviceAccountKey.json contents
+const serviceAccount = JSON.parse(process.env.FIREBASE_SERVICE_ACCOUNT_JSON);
+
+
+    if (serviceAccount && serviceAccount != null) {
         const serviceAccount = JSON.parse(fs.readFileSync('./serviceAccountKey.json', 'utf8'));
         admin.initializeApp({
             credential: admin.credential.cert(serviceAccount),