Error when deploying lambda AWS with custom domain name.

[fixanoid]

Followed instructions, set up custom domain name in the API gateway, but when landing on the custom domain I see this error:

Not Found
404
Error: Not Found
    at /var/task/app.js:42:17
    at Layer.handle [as handle_request] (/var/task/node_modules/express/lib/router/layer.js:95:5)
    at trim_prefix (/var/task/node_modules/express/lib/router/index.js:317:13)
    at /var/task/node_modules/express/lib/router/index.js:284:7
    at Function.process_params (/var/task/node_modules/express/lib/router/index.js:335:12)
    at next (/var/task/node_modules/express/lib/router/index.js:275:10)
    at /var/task/node_modules/express/lib/router/index.js:635:15
    at next (/var/task/node_modules/express/lib/router/index.js:260:14)
    at Function.handle (/var/task/node_modules/express/lib/router/index.js:174:3)
    at router (/var/task/node_modules/express/lib/router/index.js:47:12)

What did I do wrong? Thanks!