Use es6 generators to simplify async calls.

index.js

/**
 * Required node >= v0.11.2
 * usage: node --harmony index.js
 */

var fs  = require('fs');
var run = require('./run');

function readFile(filename) {
  return fs.readFile.bind(fs, filename, 'utf-8');
}

run(function* example() {
  var a = yield readFile(__filename);
  var b = yield readFile('package.json');
  var c = yield readFile('.gitignore');
  console.log(a, b, c);

  try {
    yield readFile('foo-bar.js');
  } catch (e) {
    console.log('foo-bar.js does not exists');
  }
});

run.js

var slice = [].slice;

function run(fn) {
  var gen = fn();

  function next(err, val) {
    if (err) {
      gen.throw(err);
    } else {
      var res = gen.send(val);
      if (!res.done) res.value(next);
    }
  }

  next();
}