CSS files are not served.

[cydside]

Hi,
in chapter4/4_httprouter/main.go the line

http.Handle("/assets/", http.StripPrefix("/assets/", http.FileServer(http.Dir("assets/"))))

even if I use the following code:

filesRourter := NewRouter()
filesRourter.ServeFiles("/assets/css/*filepath", http.Dir("assets/"))

doesn't allow the browser to access the css files, the pase has not a style.
I'm using go1.7.1 and the httprouter last commit is 4563b0b.
Could you please fix it?
Thanks