Static file serving is a great tutorial project in Go. I wrote mine (https://github.com/biorisk/httpfolder) to include a file upload option too, but did not add some of the nicer features, e.g., https, in your project.

So 20 or so lines of code is too tough? How much work is involved integrating this server into an app?

Not sure why you think this server was written to integrate into apps. If you can't think of a use for it, that's fine. But lots of other people do have uses for simple static web servers. Including people who don't have the knowledge, time, or patience to hand code a 20 line Go program every time they want to use one.

By integrate I meant interacting with your program, whatever that may be. With the go server, you get everything this program has without the concern of the code going stale or dying should the author abandon it.