How to add new value with same key to document

I need to write down a category and its cost in category object. Now, in my code example, I am adding the products: $50 category to the user. After execution, ‘categories’: { products: ’50$’ } is displayed in the console. But if you add products: 1000$ again, it will overwrite and output ‘categories’: { products: ‘1000$’ }. And I need to display ‘categories’: { products: ‘$50’ , products: ‘$1000’ }. How can this be implemented?

mongoClient.connect(function (err, client) {
  if (err) return console.log(err);

  const db = client.db("db");
  const col = db.collection("coll");
  col.findOneAndUpdate(
    {
      name: "User1",
    },
    {
      $set: {
        "сategories.products": "50$",
      },
    },
    function (err, result) {
      console.log(result);
      client.close();
    }
  );
});

>Solution :

Instead of

$set: {
  "сategories.products": "50$"
}

use

$addToSet: {
  сategories: {
    products: "1000$"
  }
}