/**
  * Show document page in response to the given $file.
  *
  * @param string $file
  * @return \Illuminate\Contracts\View\Factory|\Illuminate\View\View
  */
 public function show($file = '01-welcome.md')
 {
     $index = Cache::remember('documents.index', 120, function () {
         return markdown($this->document->get());
     });
     $content = Cache::remember("documents.{$file}", 120, function () use($file) {
         return markdown($this->document->get($file));
     });
     return view('documents.index', compact('index', 'content'));
 }