如何在保持对请求对象的访问的同时，对express-graphql解析器进行依赖注入？

const express = require('express');
const { graphqlHTTP } = require('express-graphql');
const { buildSchema } = require('graphql');

const schema = buildSchema(`
  type Query {
    hello: String
  }
`);

const root = {
  hello: () => 'Hello World!'
};

const app = express();

app.use('/graphql', graphqlHTTP({
  schema: schema,
  rootValue: root,
  graphiql: true
}));

const injectRequest = (req, res, next) => {
  root.request = req;
  next();
};

app.use(injectRequest);

app.listen(3000, () => {
  console.log('GraphQL server running on port 3000');
});

query {
  hello
}