function paramCallback(err) {
    var fn = paramCallbacks[paramIndex++];

    // store updated value
    paramCalled.value = req.params[key.name];

    if (err) {
      // store error
      paramCalled.error = err;
      param(err);
      return;
    }

    if (!fn) return param();

    try {
      fn(req, res, paramCallback, paramVal, key.name);
    } catch (e) {
      paramCallback(e);
    }
  }
Get all addresses in the request, optionally stopping
at the first untrusted.

@param {Object} request
@param {Function|Array|String} [trust]
@public