code: function defaultKeyGenerator(request) {
    let protocol = request.protocol;
    let host = request.get('Host');
    let url = request.originalUrl;
  
    return protocol + ':' + host + url;
  }
docs: Generates a cache key identifying the provided HTTP request and simillar
  requests that may share the same page content.
  
  @param {Express.Request} request The current express.js HTTP request.
  @return {string} The generated cache key.