here is my refrence https://github.com/awslabs/aws-mobile-appsync-sdk-js#using-authorization-and-subscription-links-with-apollo-client-v3-no-offline-support I am using apollo client version3.x

Here is code.

const auth = {
    type: 'AMAZON_COGNITO_USER_POOLS',
    jwtToken: async () => getToken()
}
const region = 'xx-xxxx-1';
const httpLink = createHttpLink({
    uri: URL,
});
const authLink = createAuthLink({
    url: URL,
    region: region,
    auth: auth
})
const wsLink = createSubscriptionHandshakeLink({ URL, region, auth }, httpLink)

const splitLink = ApolloLink.from([
    authLink,
    wsLink,
  ]);

const apollo_client = new ApolloClient({
    link: splitLink,
    cache: new InMemoryCache(),
});