Ask HN: How would you code a Webserver like Nginx?

Loaded question, I know. I am fascinated with how web servers work and wondering if you all can share some resources on how to write your own web server. I google a bunch. I am interested in using Golang ideally (fun project for now). I want to build it in such a way that I can add my own rules like nginx and not have nginx at all as a proxy.

So, any ideas/tips/resources on how one would go about writing a web server in Go ? The hello world examples are a good start but how do you parse URLs etc ?