Explicitly pass the handler

[Kikobeats]

Since the codebase is not returning the next explicitly, when you have an async interface involving this library, the Promise exit early getting the implicit undefined until now returned.

[UlisesGascon]

@carpasse can you have a look?

[carpasse]

I think what @Kikobeats needs can probably be achieved by creating a wrapper around the responseTime middleware:

function responseTimeWrap(opts) {
  var _responseTime = responseTime(opts);

  return function (req, res, next) {
    return new Promise((resolve, reject) => {
      try {
        _responseTime(req, res, resolve);
      } catch (err) {
        reject(err)
      }
    })
    .catch(next)
    .then(next);
  };
}

We should probably wait until Express next Major v5 supports promises natively before implementing such a change.