How to use the elasticsearch.default.Client function in elasticsearch

import { version as agentVersion } from '../../../package.json';
import { default as proxy } from 'proxy-agent';
import { default as https } from 'https';

const agentGroup = process.env.GTM_AGENT_GROUP || 'default';

AWS.config.update({ region: process.env.GTM_AWS_REGION });

let log = AgentLogger.log();
const EVENTS_TABLE = process.env.GTM_DYNAMO_TABLE_EVENTS;
let INITIAL_DATA = [];
let EventMetricStream;

let elastic;
if (process.env.GTM_ELASTIC_HOST && process.env.GTM_ELASTIC_PORT) {
    elastic = new elasticsearch.Client({
        host: `${process.env.GTM_ELASTIC_HOST}:${process.env.GTM_ELASTIC_PORT}`,
        log: 'info'
    });
}

if (process.env.IAM_ENABLED) {
    AWS.config.update({
        httpOptions: {
            agent: proxy(process.env.HTTP_PROXY)
        }
    });
}

async function configureRoutes(app) {
    let ddb;
    if (process.env.GTM_DYNAMO_VPCE) {