CachedFile v2

struct CachedFile(NamedFile);

impl<'r> Responder<'r> for CachedFile {
    fn respond_to(self, req: &Request) -> response::Result<'r> {
        let nfile_response = self.0.respond_to(req)?;
        Response::build_from(nfile_response)
            .raw_header("Cache-control", "max-age=86400") //  24h (24*60*60)
            .ok()
    }
}

#[get("/resources/<file..>")]
fn files(file: PathBuf) -> Option<CachedFile> {
    NamedFile::open(Path::new("resources/").join(file)).ok().map(|nf| CachedFile(nf))
}