why does terminal tell me on line 8 that the callback must be a function? what am i doing wrong here?

I have included an image of the error that I'm getting in my terminal. I have tried as much as I can to resolve the issue, but nothing seems to help. Attached is a link to my github repository where you will find the application. The file in question is "server.js."

https://github.com/malekmekdashi/Note-Taker

https://i.stack.imgur.com/OakN4.png