code: function patchFetchForRelativeURLs(instance) {
    const fastboot = instance.lookup('service:fastboot');
    const request = fastboot.get('request');
    // Prember is not sending protocol
    const protocol = request.protocol === 'undefined:' ? 'http:' : request.protocol;
    // host is cp
    setupFastboot(protocol, request.get('host'));
  }
docs: To allow relative URLs for Fastboot mode, we need the per request information
  from the fastboot service. Then we set the protocol and host to fetch module.