AWS, RDS（PostgreSQL）, Lambda（Node.JS）の組み合わせで30秒ぐらいコネクションを使っていると落ちる

下記のようにしていると落ちる。

'use strict'

var DBDao = require("../utils/dao").DBDao;

class Dummy {
    static async exec(i) {
        console.log("----------------")
        var sql = `select * from sometable;`

        for (var i = 0; i < 1000000; i++) {
            var dao = new DBDao();
            console.log(i);
            var results = await dao.query(sql, []);
                // .then((res) => {
                //     return new Promise(function (resolve, reject) {
                //         // dao.close();
                //         resolve();
                //     });
                // })
            console.log(results.length);
            dao.close();
        }
    }
}

module.exports.Dummy = Dummy;

下記のようなエラーで落ちる。

select * from itemtable; []
248
781
select * from itemtable; []
248
782
select * from itemtable; []
query error Connection terminated by user Error: Connection terminated by user
    at Client.end (/Users/yousan/git/test/node_modules/pg/lib/client.js:402:36)
    at Pool._remove (/Users/yousan/git/test/node_modules/pg-pool/index.js:135:12)
    at Timeout.setTimeout (/Users/yousan/test/node_modules/pg-pool/index.js:38:12)
    at ontimeout (timers.js:460:11)
    at tryOnTimeout (timers.js:298:5)
    at Timer.listOnTimeout (timers.js:261:5)
error:  Error: Connection terminated by user
    at Client.end (/Users/yousan/git/test/node_modules/pg/lib/client.js:402:36)
    at Pool._remove (/Users/yousan/git/test/node_modules/pg-pool/index.js:135:12)
    at Timeout.setTimeout (/Users/yousan/git/test/node_modules/pg-pool/index.js:38:12)
    at ontimeout (timers.js:460:11)
    at tryOnTimeout (timers.js:298:5)
    at Timer.listOnTimeout (timers.js:261:5)

時間を測ると30秒ぐらいでおちている。
引き続き調査中…。