Fix slow exiting and remove stray 'RUN ls'

backend/Dockerfile

@@ -6,5 +6,4 @@ RUN yarn install
 
 COPY src src/
 COPY data data/
-RUN ls
 CMD ["node", "src/index.js"]

backend/src/app.js

@@ -14,9 +14,8 @@ const io = socketIO(server);
 
 app.get('/state', (req, res) => res.send('<pre>' + JSON.stringify(state) + '</pre>'));
 
-process.on('SIGINT', function() {
-    process.exit();
-});
+process.on('SIGINT', () => process.exit());
+process.on('SIGTERM', () => process.exit());
 
 module.exports = {
     app, server, io