Small error

src/notificationService.ts

@@ -44,7 +44,7 @@ export class NotificationService {
 
         const encrypted = this.encrypt(subscription.keys.p256dh, subscription.keys.auth, payload);
 
-        const vapidHeaders = this.vapidService.createVapidAuthHeader();
+        const vapidHeaders = await this.vapidService.createVapidAuthHeader();
 
         const parsedUrl = new URL(subscription.endpoint);
         const options: https.RequestOptions = {