static url :`/files/index.html` and `/files/` not handled

[pedia]

url :/files/index.html and /files/ not handled.

/files/ 404

/files/index.html redirected by fs.

@dimfeld How can we handle /files/?

contextMux = app.TreeMux.UsingContext()
contextMux.GET("/files/*", http.FileServer(Http.Dir(uploadPath)))

Originally posted by @pedia in #78 (comment)