post-execution middleware is failing to be called

[chemdrew]

Inside the request handler the next callback is not being called on completion

This does not allow for using the after event in restify res.on('after', () ={}) or doing middleware chaining in express

app.use(<pre-execution middleware>);

app.use('/graphql', graphqlHTTP({
  schema: schema,
}));

app.use(<post-execution middleware>);

Could we get this added in by default or add a toggle in the options to forward the middleware?
I'll create the PR if this is deemed valid.
Thanks!

[chemdrew]

easy fix on server implementation - closing issue

const graphqlHandler = (req, res, next) => {
  const graphqlHTTPHandler = graphqlHTTP({
    schema: schema,
    graphiql: true
  });
  graphqlHTTPHandler(req, res).then(() => {
    next();
  }).catch((e) => {
    next(e);
  });
};

server.get('/graphql', graphqlHandler);
server.post('/graphql', graphqlHandler);

[vivekfyi]

It works fine but i am not able to set anything to response using post middle-wares as response is already sent by graphql . #279 (comment) this solves it using a response proxy, but still not a standard approach.