myblog-express 的router合併

router middleware
http://www.expressjs.com.cn/4x/api.html#express

var express = require('express');
var router = express.Router([options]);

var express = require('express');
var app = express();
app.use('/calendar', router);

require等於插入代碼執行

const routers = require('./routes')
routers(app) //只有index是function（app）
module.exports = function (app) {
app.use('/signup', require('./signup'))
}