Some problem with no response

It's my code. The hello schema can work, but the User no response with fetch. can you help me ?
[Project Url: https://github.com/Shafley/helloApp](https://github.com/Shafley/helloApp)
```js
// createModel2Schema.js
import mongoose, { Schema } from 'mongoose'
import composeWithMongoose from 'graphql-compose-mongoose'

export default (name, schema, opts = {}) => composeWithMongoose(mongoose.model(name, new Schema(schema)), opts)

// User.js
import createModel2Schema from './createModel2Schema'
import { GQC } from 'graphql-compose'

const UserTC = createModel2Schema('User', {
name: String,
age: Number
})

GQC.rootQuery().addFields({
userById: UserTC.getResolver('findById'),
userByIds: UserTC.getResolver('findByIds'),
userOne: UserTC.getResolver('findOne'),
userMany: UserTC.getResolver('findMany'),
userCount: UserTC.getResolver('count'),
userConnection: UserTC.getResolver('connection'),
userPagination: UserTC.getResolver('pagination'),
})

GQC.rootMutation().addFields({
userCreate: UserTC.getResolver('createOne'),
userUpdateById: UserTC.getResolver('updateById'),
userUpdateOne: UserTC.getResolver('updateOne'),
userUpdateMany: UserTC.getResolver('updateMany'),
userRemoveById: UserTC.getResolver('removeById'),
userRemoveOne: UserTC.getResolver('removeOne'),
userRemoveMany: UserTC.getResolver('removeMany'),
})

export default GQC.buildSchema()

// server.js
import Koa from 'koa'
import cors from '@koa/cors'
import KoaRouter from 'koa-router'
import koaBody from 'koa-bodyparser'
import { graphqlKoa } from 'apollo-server-koa'
import { makeExecutableSchema } from 'graphql-tools'
import koaPlayground from 'graphql-playground-middleware-koa'
import mongoConnect from './mongoConnect'
import { User } from './Models'

const db = mongoConnect()

const schema = makeExecutableSchema({
typeDefs: `
type Query {
hello: String!
}
schema {
query: Query
}
`,
resolvers: {
Query: {
hello: () => 'world'
}
}
})

const app = new Koa()
const router = new KoaRouter()
const port = process.env.PORT || 3000

app.use(cors())
app.use(koaBody())

// koaBody is needed just for POST.
// router.post('/graphql', graphqlKoa({ schema: User }))
router.post('/graphql', graphqlKoa({ schema }))

router.all('/playground', koaPlayground({
endpoint: '/graphql'
}))

app.use(router.routes())
app.use(router.allowedMethods())
app.listen(port, () => {
console.log(`\n👉 Serving the GraphQL Playground on http://localhost:${port}/playground`)
console.log(`👉 Serving the GraphQL api endpoint on http://localhost:${port}/graphql\n`)
})
```