Error: connect ECONNREFUSED 127.0.0.1:5432 on docker code example

Example 1: docker posgres connect ECONNREFUSED 127.0.0.1:5432

const pgPool = new Pool(pgConfig);
const pgPoolWrapper = {
    async connect() {
        for (let nRetry = 1; ; nRetry++) {
            try {
                const client = await pgPool.connect();
                if (nRetry > 1) {
                    console.info('Now successfully connected to Postgres');
                }
                return client;
            } catch (e) {
                if (e.toString().includes('ECONNREFUSED') && nRetry < 5) {
                    console.info('ECONNREFUSED connecting to Postgres, ' +
                        'maybe container is not ready yet, will retry ' + nRetry);
                    // Wait 1 second
                    await new Promise(resolve => setTimeout(resolve, 1000));
                } else {
                    throw e;
                }
            }
        }
    }
};

Example 2: Connection error: connect ECONNREFUSED 127.0.0.1:5432

database system is ready to accept connections