koa.js error handling sample

error.js

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

app.use(function *(next){
  try {
    yield next;
  }
  catch (err) {
    console.log(err);
    this.status = err.status || 500;
    this.body = err.message || require('http').STATUS_CODES[this.status];
  }
});

app.use(function *(next){
  throw new Error('some error');
});

app.listen(3000);

run.sh

node --harmony error.js
[Error: some error]