TypeError: Cannot read property 'send' of undefined
    at /home/runner/chat-example/index.js:17:10
    at Layer.handle [as handle_request] (/home/runner/chat-example/node_modules/express/lib/router/layer.js:95:5)
    at next (/home/runner/chat-example/node_modules/express/lib/router/route.js:137:13)
    at Route.dispatch (/home/runner/chat-example/node_modules/express/lib/router/route.js:112:3)
    at Layer.handle [as handle_request] (/home/runner/chat-example/node_modules/express/lib/router/layer.js:95:5)
    at /home/runner/chat-example/node_modules/express/lib/router/index.js:281:22
    at Function.process_params (/home/runner/chat-example/node_modules/express/lib/router/index.js:335:12)
    at next (/home/runner/chat-example/node_modules/express/lib/router/index.js:275:10)
    at expressInit (/home/runner/chat-example/node_modules/express/lib/middleware/init.js:40:5)
    at Layer.handle [as handle_request] (/home/runner/chat-example/node_modules/express/lib/router/layer.js:95:5)