node.js mysql2 pool will leak connection if error occured

mysql2_pool_leak.js

"use strict";

const mysql2     = require('mysql2'),
      co         = require('co');

const pool = mysql2.createPoolPromise({
    host: "127.0.0.1",
    port: 3306,
    user: 'root',
    password: "",
    database: 'test',
    charset: 'UTF8MB4_GENERAL_CI'
});

co(function* () {
    yield pool.query('CREATE TABLE IF NOT EXISTS test ( name VARCHAR(32) NOT NULL, PRIMARY KEY(name))');
    for(let i = 0; i < 15; ++i) {
        try {
            yield pool.query('INSERT INTO test SET name="hello"');
        } catch (e) {
            if (e.code == 'ER_DUP_ENTRY') {
                console.error(i + ': ER_DUP_ENTRY' + e.stack);
            } else {
                throw e;
            }
        }
    }
}).then(function () {
    console.warn("end");
    process.exit(0);
}, function (err) {
    console.error({error: err.stack}, "error");
    process.exit(1);
}).catch(function (e) {
    console.error({exception: e.stack}, "exception");
    process.exit(1);
});