const
    MongoClient = require("mongodb").MongoClient;

const mongodb_con_str =
    "mongodb://" +
    "localhost:27018,localhost:27019,localhost:27020" +
    "/test" +
    "?replicaSet=rs0";

const mongodb_con_opts = { "useNewUrlParser": true };



MongoClient.connect(mongodb_con_str, mongodb_con_opts)

.then(

    mongo => Promise.reject()

    .then(
        _ => console.log("Program OK"),
        _ => console.log("Program error")
    )

    // Adding a delay allows MongoClient.close()
    // to close the connection.

    //.then(_ => new Promise(r => setTimeout(r, 0)))

    .then(_ => mongo.close()))

.catch(e => console.log("Program ended with error", e));