Add caching middlware for static files

cmd/web/middleware.go

@@ -29,3 +29,10 @@ func (app *application) logRequest(next http.Handler) http.Handler {
 		next.ServeHTTP(w, r)
 	})
 }
+
+func (app *application) cacheStatic(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Cache-Control", "public, max-age=86400")
+		next.ServeHTTP(w, r)
+	})
+}