Getting“TypeError:必须提供机密字符串。”在带护照的NodeJS申请中。js和Express Session作为中间件

有人能解释一下中间件在哪里需要一个秘密字符串吗? 此外,如果我在passport中设置了密钥/值对。会话选项我仍然收到相同的错误消息

    // using pug since a view engine is required by express
    app.set('views', __dirname)
    app.set('view engine', 'pug')

    app.use(cookieParser(secretConfig))
    // parse application/json
    app.use(bodyParser.json())

    // parse application/x-www-form-urlencoded
    app.use(bodyParser.urlencoded({ extended: false }))


    app.use(passport.initialize());
    app.use(passport.session({
      resave: false,
      saveUninitialized: true,
      failureFlash: true
    }));

    //app.use(flash());

    // Load the REST endpoints
    app.use('/api', require('./endpoints/whatever/router'))
    app.use('/api', require('./endpoints/login/router'))

    // app.use('/api', require('./users/router'))
    // Repeat the above line for additional model areas ("deals", "vehicles",         etc)


    app.use('/graphql', graphqlHTTP({
        schema: schema,
        rootValue: root,
        graphiql: true
    }));