mongo-init.js

db.getSiblingDB('admin').auth(
    process.env.MONGO_INITDB_ROOT_USERNAME,
    process.env.MONGO_INITDB_ROOT_PASSWORD
);

db.createUser({
    user: process.env.MONGO_USER,
    pwd: process.env.MONGO_PASSWORD,
    roles: [
        {
            role: "readWrite",
            db: process.env.MONGO_DB
        }
    ],
    mechanisms: ["SCRAM-SHA-1", "SCRAM-SHA-256"]
});