feat: additional error checks after queue subscribe

internal/sshportalapi/server.go

@@ -56,11 +56,21 @@ func ServeNATS(ctx context.Context, stop context.CancelFunc, log *zap.Logger,
 	}
 	defer nc.Close()
 	// set up request/response callback for sshportal
-	_, err = nc.QueueSubscribe(SubjectSSHAccessQuery, queue,
+	sub, err := nc.QueueSubscribe(SubjectSSHAccessQuery, queue,
 		sshportal(ctx, log, nc, l, k))
 	if err != nil {
 		return fmt.Errorf("couldn't subscribe to queue: %v", err)
 	}
+	// additional error checks
+	if err = nc.Flush(); err != nil {
+		return fmt.Errorf("couldn't flush connection after subscribe: %v", err)
+	}
+	if err = nc.LastError(); err != nil {
+		return fmt.Errorf("connection error after subscribe: %v", err)
+	}
+	if !sub.IsValid() {
+		return fmt.Errorf("invalid subscription")
+	}
 	// wait for context cancellation
 	<-ctx.Done()
 	// drain and log errors