http.FileServer response with wrong mime "Content-Type"

Question

I'm using http.FileServer to serve a directory of mp3 files, which my template then src in javascript. The response, however, uses the Content-Type text/html instead of audio/mpeg. How do I set the mime type which the FileServer responds with, I saw this question Setting the 'charset' property on the Content-Type header in the golang HTTP FileServer , but I'm still not sure how to override the mime type.

My code looks like the following:

fs := http.FileServer(http.Dir(dir))
http.Handle("/media", http.StripPrefix("/media", fs))
http.HandleFunc("/", p.playlistHandler)
http.ListenAndServe(":5177", nil)

and the error I get is:

HTTP "Content-Type" of "text/html" is not supported. Load of media resource http://localhost:5177/media/sample1.mp3 failed.

Answer 1

It's not a problem of content types. Your fs handler isn't getting called when you request the mp3. You need to add a / to your pattern /media and the strip prefix like this

http.Handle("/media/", http.StripPrefix("/media/", fs))

The reason is in the documentation of net/http.ServeMux

Patterns name fixed, rooted paths, like "/favicon.ico", or rooted subtrees, like "/images/" (note the trailing slash). Longer patterns take precedence over shorter ones, so that if there are handlers registered for both "/images/" and "/images/thumbnails/", the latter handler will be called for paths beginning "/images/thumbnails/" and the former will receive requests for any other paths in the "/images/" subtree.

With just /media you're registering a handler for a path but with a trailing slash it considers it a rooted subtree and will serve requests under that tree.