code: protected function normalizeTrailingSlash($pathInfo, $suffix)
      {
          if (substr($suffix, -1) === '/' && substr($pathInfo, -1) !== '/') {
              $pathInfo .= '/';
          } elseif (substr($suffix, -1) !== '/' && substr($pathInfo, -1) === '/') {
              $pathInfo = rtrim($pathInfo, '/');
          }
  
          return $pathInfo;
      }
docs: Adds or removes trailing slashes from $pathInfo depending on whether the $suffix has a
  trailing slash or not.
  @param string $pathInfo raw path info.
  @param string $suffix
  @return string normalized path info.