Wrap koa-like generators to express-like callbacks.

wrap-generator.js

var co = require('co')

/**
 * Wrap koa-like generators to express-like callbacks.
 *
 * @param {GeneratorFunction} fn
 * @return {Function}
 */

modules.exports = function wrap(fn) {
  return function(req, res, next) {
    co(function*() {
      yield* fn(req, res)
    })
    .catch(next)
  }
}