Is there anyway to return response to client when mongodb is stopped in nodejs http requests?

I have an express app and using Mongodb. Here is my 2 connections with database :

const mongoose = require("mongoose");

try {
  const db1 = mongoose.createConnection(
    `mongodb://${process.env.DB_DOMAIN}/${process.env.DB_1_NAME}`,
    {
      authSource: "admin",
      user: process.env.DB_USERNAME,
      pass: process.env.DB_PASSWORD,
      useNewUrlParser: true,
      tls: true,
      sslValidate: false,
      connectTimeoutMS: process.env.DB_TIMEOUT, // 15000
    }
  );

  const db2 = mongoose.createConnection(
    `mongodb://${process.env.DB_DOMAIN}/${process.env.DB_2_NAME}`,
    {
      authSource: "admin",
      user: process.env.DB_USERNAME,
      pass: process.env.DB_PASSWORD,
      useNewUrlParser: true,
      tls: true,
      sslValidate: false,
      connectTimeoutMS: process.env.DB_TIMEOUT, // 15000
    }
  );
  module.exports = {
    db1,
    db2,
  };
} catch (err) {
  console.log(err);
}

The Mongodb service is stopped. When I request to do something, it takes long time and doesn't return any error. How can I handle it?