$ npm install koa

$ npm install -g koa

var koa = require('koa');
var app = koa();

// logger

app.use(function *(next){
 var start = new Date;
 yield next;
 var ms = new Date - start;
 console.log('%s %s - %s', this.method, this.url, ms);
});

// response

app.use(function *(){
 this.body = 'Hello World';
});

app.listen(3000);

alias node='node --harmony'

var koa = require('koa');
var app = koa();

// x-response-time
app.use(function *(next){
 // (1) 进入路由
 var start = new Date;
 yield next;
 // (5) 再次进入 x-response-time 中间件，记录2次通过此中间件「穿越」的时间
 var ms = new Date - start;
 this.set('X-Response-Time', ms + 'ms');
 // (6) 返回 this.body
});

// logger
app.use(function *(next){
 // (2) 进入 logger 中间件
 var start = new Date;
 yield next;
 // (4) 再次进入 logger 中间件，记录2次通过此中间件「穿越」的时间
 var ms = new Date - start;
 console.log('%s %s - %s', this.method, this.url, ms);
});

// response
app.use(function *(){
 // (3) 进入 response 中间件，没有捕获到下一个符合条件的中间件，传递到 upstream
 this.body = 'Hello World';
});

app.listen(3000);

.middleware1 {
 // (1) do some stuff
 .middleware2 {
  // (2) do some other stuff
  .middleware3 {
   // (3) NO next yield !
   // this.body = 'hello world'
  }
  // (4) do some other stuff later
 }
 // (5) do some stuff lastest and return
}

var wrapper = require('co-mysql'),
 mysql = require('mysql');
var options = {
  host : 'localhost',
  port : 3306 ,
  database : 'test',
  user: 'root',
  password : 'rootroot'
};

var pool = mysql.createPool(options),
 p = wrapper(pool);

...
 var rows = yield p.query('SELECT 1');
 yield this.render('index', {
    title: rows[0].fieldName
  });
...
})();

var promisify = require("promisify-node");
var db = promisify("myDbHelper");
...
var rows = yield db.getById('tableName', {id:1});
  yield this.render('index', {
    title: rows[0].fieldName
  });
...

var genify = require('thunkify-wrap').genify;
var db = genify("myDbHelper");
...
var rows = yield db.getById('tableName', {id:1});
  yield this.render('index', {
    title: rows[0].fieldName
  });
...

var config = require('./dbconfig');

var options = {
  'host': config.db_host,
  'port': config.db_port,
  'database': config.db_name,
  'user': config.db_user,
  'password': config.db_passwd
}

var mysql = require('mysql');
var pool = mysql.createPool(options);

//内部对mysql的封装，执行sql语句
function execQuery(sql, values, callback) {
  var errinfo;
  pool.getConnection(function(err, connection) {
    if (err) {
      errinfo = 'DB-获取数据库连接异常！';
      throw errinfo;
    } else {
      var querys = connection.query(sql, values, function(err, rows) {
        release(connection);
        if (err) {
          errinfo = 'DB-SQL语句执行错误:' + err;
          callback(err);
        } else {
          callback(null,rows);    //注意：第一个参数必须为null
        }
      });
    }
  });
}

function release(connection) {
  try {
    connection.release(function(error) {
      if (error) {
        console.log('DB-关闭数据库连接异常！');
      }
    });
  } catch (err) {}
}
//对外接口返回Promise函数形式
exports.getById = function(tablename, id){
  return new Promise(function(resolve, reject){
    var values = {id:id};
    var sql = 'select * from ?? where ?';
    execQuery(sql,[tablename, values], function(err, rows){
      if(err){
        reject(err);
      }else{
        resolve(rows);
      }
    })
  });
}
routes/index.js

var db = require("../dbHelper");
...
var rows = yield db.getById('tableName', {id:1});
  yield this.render('index', {
    title: rows[0].fieldName
  });
...