To avoid restart manually install the nodemon cli :
sudo yarn global add nodemon
Now run the app like that
nodemon app.js
If you want usefull debug message for your daemon you can launch like it
DEBUG=express:* nodemon app.js
curl http://127.0.0.1:3000/doc
curl http://127.0.0.1:3000
curl http://127.0.0.1:3000/api