https://docs.amplify.aws/lib/graphqlapi/subscribe-data/q/platform/js#using-amplify-graphql-client

aws-appsync.js

import Amplify, { API, graphqlOperation } from "aws-amplify";
// import API from '@aws-amplify/api';
import awsconfig from './aws-exports';

Amplify.configure(awsconfig) // *not sure
API.configure(awsconfig);

// Subscribe to creation of Todo
const SubscribeToEventComments = `subscription subscribeToComments {
  subscribeToComments {
    commentId
    content
  }
}`;

const subscription = API.graphql({
  query: SubscribeToEventComments,
  variables: {}
}).subscribe({
  next: (eventData) => console.log(eventData)
});

// Stop receiving data updates from the subscription
subscription.unsubscribe();

aws-exports.js

// Sample file: https://github.com/clayton13/HeadsUpAngel/blob/3546992cf1c7ffc2b0db04b915b87cba58b19d0f/src/aws-exports.js
var config = {
    APIKEY: 'key',
    REGION: 'us-west-2',
    TYPE: 'API_KEY',
    ENDPOINT: 'endpoint',
};
export default config;