Node.js + Mongoose: How to use a virtual property to associate an ObjectID with the property?

Question

I'm trying to access a MongoDB database using Node.js and Mongoose.

I created a virtual property in Schema called username. See the code that follows.

const mongoose = require("mongoose");
const User = require("../models/user");

const datatypes = ['temperature', 'humidity'];

const nodeSchema = new mongoose.Schema(
    {
        MACAddress: {
            type: String,
            required: true,
            trim: true,
            uppercase: true,
            match: /^([0-9A-F]{2}[:-]){5}([0-9A-F]{2})$/,
        },
        alias: {
            type: String,
            trim: true,
        },
        coordinates: {
            type: String,
            required: false,
            match: /^(\-?\d+(\.\d+)?),\s*(\-?\d+(\.\d+)?)$/,
        },
        address: {
            type: String,
            required: false,
        },
        userID: {
            type: mongoose.Types.ObjectId,
        },
        nodeType: {
            type: String,
            enum: ['router', 'node'],
            default: 'node',
        },
        dataTypes: {
            type: [String],
            enum: datatypes,
            required: true,
        }
    },
    {
        timestamps: true,
    }
);

The virtual property is used to set the userID property. See the code that follows.

// virtual field
nodeSchema.virtual("username").set(async function (username) {
    this.userID = await this.getUserID(username);
});

// methods
nodeSchema.methods = {
    getUserID: function (username) {
        if (!username) return null;

        return User.find({username: username}).then(userDoc => userDoc[0]._id);
    },
};

To add a new document to the database, I am using the following code.

const newNode = new Node(newNodeData);

            newNode.save().then( (node) => {
                    console.log(node.userID)
                }
            )

The problem is this... Calling the User.find function returns a promise. Even using await (see previous code), newNode.save() saves the document in the database without the userID property.

If I change the code to the following snippet, which doesn't use promise, the userID property is saved in the database with no problem. However, this is not what I want.

// virtual field
nodeSchema.virtual("username").set(async function (username) {
    let ObjectId = mongoose.Types.ObjectId;
    this.userID = new ObjectId("6245e896afe465a25047302e");
});

How can I force newNode.save() to wait for the promise result before saving the document to the database?