gistfile1.txt

// express method
app.use(async function (req, res, next) {
  try {
    let flux = new Flux();
    var {HandlerComponent, state} = await AuxService.runReactRouter(reactRoutes, req.url);

    await AuxService.performRouteHandlerStaticMethod(state.routes, 'routerWillRun', {state, flux, req});
    ...
  }
  ...
}


// app component
class App extends React.Component {
  static async routerWillRun({flux, state, req}) {
    await flux.getActions('session').getSession(req);
  }
  
  // rendering ...
}

// session actions
class SessionActions extends AppActions {

  getSession(req) {
    // using req object here to pass cookies
    return this.apiGet('/api/session/get', req);
  }

}