Execute async within context of Koa middleware

app.js

function loadPageAsync() {
  return new Promise(function(resolve, reject) {
    request = http.get({
        host: 'www.google.com',
        path: '/boom'
    }, function(response) {
      var body = '';
      response.on('data', function(d) {
          body += d;
      });
      response.on('end', function() {
        response.body = body;
        resolve(response);
      });
    });
    request.on('error', function(err) {
      console.log('ERROR');
      reject(err);
    });
  });
}

app.use(function *(){
  var response;
  try {
    response = yield loadPageAsync();
  } catch (err) {
    console.log(err);
    this.throw(err);
  }
  console.log('Code: ' + response.statusCode);
  this.body = response.body;
  if (response.statusCode < 200 || response.statusCode >= 300) {
    this.throw(response.statusCode, response.statusMessage);
  }
});