GraphQL Subscriptions Error: "The \"properties\" argument must be of type Array. Received type object" - graphql

Question

I am trying to implement a simple API with GraphQL. My queries and my mutations are in place and working, but now I'm trying to include subscriptions as well.
I already added the subscription in the schema, I included the event publish in the addUser mutation and defined the subscribe function for the subscription type.
Now, when I am trying to run a subscription query in the graphiql in-browser IDE, I get this error:
"The \"properties\" argument must be of type Array. Received type object"
Attached is the schema object. Did I configured something wrong or am I missing something? Thanks!
P.S I also need to mention that I am using mongoose to store the data on an a mongo instance, hence the entities.
import {
GraphQLFloat,
GraphQLID,
GraphQLInt,
GraphQLList,
GraphQLNonNull,
GraphQLObjectType,
GraphQLSchema,
GraphQLString
} from 'graphql';
// models
import UserType from '../types/user/UserType';
import AccountType from '../types/account/AccountType';
import TransactionType from '../types/transaction/TransactionType';
// entities
import User from '../entities/user/user';
import Account from '../entities/account/account';
import Transaction from '../entities/transaction/transaction';
// subscriptions
import { PubSub } from 'graphql-subscriptions';
// subscriptions
const pubsub = new PubSub();
const USER_CREATED = 'user_created';
// the acceptable starting point of our graph
const RootQueryType = new GraphQLObjectType({
name: 'RootQueryType',
fields: () => ({
// query individual entities in the database
user: {
type: UserType,
description: 'The current user identified by an id',
args: {
id: {
type: GraphQLID
}
},
resolve(parent, args) {
return User.findById(args.id);
}
},
account: {
type: AccountType,
description: 'Details about the account in question identified by an id',
args: {
id: {
type: GraphQLID
}
},
resolve(parent, args) {
return Account.findById(args.id);
}
},
transaction: {
type: TransactionType,
description: 'Details about the transaction in question identified by an id',
args: {
id: {
type: GraphQLID
}
},
resolve(parent, args) {
return Transaction.findById(args.id);
}
},
// query all entities in the database
users: {
type: new GraphQLList(UserType),
resolve: (parent, args) => {
return User.find({});
}
},
accounts: {
type: new GraphQLList(AccountType),
resolve: (parent, args) => {
return Account.find({});
}
},
transactions: {
type: new GraphQLList(TransactionType),
resolve(parent, args) {
return Transaction.find({});
}
}
})
});
const MutationType = new GraphQLObjectType({
name: 'Mutation',
fields: () => ({
addUser: {
type: UserType,
args: {
name: {
type: new GraphQLNonNull(GraphQLString)
},
age: {
type: new GraphQLNonNull(GraphQLInt)
},
email: {
type: new GraphQLNonNull(GraphQLString)
}
},
resolve(parent, args) {
let user = new User({
name: args.name,
age: args.age,
email: args.email
});
pubsub.publish(USER_CREATED, {
newUser: user
});
return user.save();
}
},
addAccount: {
type: AccountType,
args: {
currency: {
type: new GraphQLNonNull(GraphQLString)
},
balance: {
type: new GraphQLNonNull(GraphQLFloat)
},
holderId: {
type: new GraphQLNonNull(GraphQLString)
}
},
resolve(parent, args) {
let account = new Account({
currency: args.currency,
balance: args.balance,
holderId: args.holderId
});
return account.save().then(() => console.log('user created'));
}
},
addTransaction: {
type: TransactionType,
args: {
sourceAccountId: {
type: new GraphQLNonNull(GraphQLString)
},
targetAccountId: {
type: new GraphQLNonNull(GraphQLString)
},
amount: {
type: new GraphQLNonNull(GraphQLFloat)
}
},
resolve(parent, args) {
let transaction = new Transaction({
sourceAccountId: args.sourceAccountId,
tagetAccountId: args.tagetAccountId,
timestamp: new Date(),
amount: args.amount
});
Account.findById(args.sourceAccountId, (err, account) => {
if (!err) {
account.balance -= args.amount;
return account.save();
}
});
Account.findById(args.targetAccountId, (err, account) => {
if (!err) {
account.balance += args.amount;
return account.save();
}
});
return transaction.save();
}
}
})
});
const SubscriptionType = new GraphQLObjectType({
name: 'Subscription',
fields: () => ({
newUser: {
type: UserType,
description: 'This subscription is going to provide information every time a new user creation event fires',
resolve: (payload, args, context, info) => {
console.table(payload, args, context, info); // debugging
return payload;
},
subscribe: () => pubsub.asyncIterator(USER_CREATED)
}
})
});
const schema = new GraphQLSchema({
query: RootQueryType,
mutation: MutationType,
subscription: SubscriptionType
});
export default schema;
I expect that when I run the subscription query, it will run listening for events being published and when from another tab I will run a mutation to add a new user, the first tab will catch the event and return details of the user in the payload.