Apollo GraphQL v3 subscription returning null - node.js

Question

I'm having a super hard time with setting up subscriptions in apollo-server. It's listening, I can make the mutation and query the result. But, the subscription for the same data returns null every time. Here are the important parts of my code:
import { Storage } from "#google-cloud/storage"
import { createError } from "apollo-errors"
import { ApolloServer, gql, PubSubEngine } from "apollo-server-express"
import { PubSub } from "apollo-server"
import cors from "cors"
import express from "express"
import jwt from "express-jwt"
import jwksRsa from "jwks-rsa"
import neo4j from "neo4j-driver"
import { initializeDatabase } from "./initialize"
import { typeDefs } from "./schema.js"
import { createServer } from "HTTP"
const pubsub = new PubSub()
const app = express()
const messages = []
const resolvers = {
Mutation: {
postMessage(parent, { user, content }, context) {
const id = messages.length
messages.push({
id,
user,
content,
})
pubsub.publish("test", {
messages,
})
return id
},
},
Query: {
messages: () => messages,
},
Subscription: {
messages: {
subscribe: (parent, args, context) => {
return pubsub.asyncIterator("test")
},
},
},
}
const neoSchema = new Neo4jGraphQL({
typeDefs,
resolvers,
config: {
jwt: {
secret: process.env.NEO4J_GRAPHQL_JWT_SECRET,
},
},
debug: true,
})
const NEO4J_USER = process.env.NEO4J_USER
const NEO4J_PASS = process.env.NEO4J_PASS
const NEO4J_URI = process.env.NEO4J_URI
const driver = neo4j.driver(NEO4J_URI, neo4j.auth.basic(NEO4J_USER, NEO4J_PASS))
const init = async (driver) => {
await initializeDatabase(driver)
}
try {
init(driver).catch((e) => console.log(e))
console.log("ne4j initialized...")
} catch (error) {
console.error(`Failed to property initialize database`, error)
}
const apolloServer = new ApolloServer({
schema: neoSchema.schema,
context: ({ req }) => {
return {
driver,
pubsub,
req,
}
},
subscriptions: {
onConnect: async (connectionParams, webSocket, context) => {
console.log("xxx")
console.log(connectionParams)
},
onDisconnect: (websocket, context) => {
console.log("WS Disconnected!")
},
path: "/graph",
},
introspection: true,
playground: true,
})
apolloServer.applyMiddleware({ app, path: "/graph" })
const httpServer = createServer(app)
apolloServer.installSubscriptionHandlers(httpServer)
const port = process.env.PORT || 8080
httpServer.listen({ port }, () => {
console.log(`Server is ready at http://localhost:${port}${apolloServer.graphqlPath}`)
console.log(`Subscriptions ready at ws://localhost:${port}${apolloServer.subscriptionsPath}`)
})
And from my schema:
export const typeDefs = gql`
type Message {
id: ID!
user: String!
content: String!
}
type Query {
messages: [Message!]
}
type Subscription {
messages: [Message!]
}
type Mutation {
postMessage(user: String!, content: String!): ID!
}
`
If I execute a mutation on postMessage, then query messages, I get the expected data back. However, when I run the subscription from the client, I get
{
"data": {
"messages": null
}
}
What's happening here? What am I missing? Is there something missing in my server setup? Are my pubsub and subscriptions code off?