MongoError: Authentication failed.
    at Function.MongoError.create (/home/user/ashish/FitnessApp/backend/node_modules/mongoose/node_modules/mongodb-core/lib/error.js:31:11)
    at /home/user/ashish/FitnessApp/backend/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:497:72
    at authenticateStragglers (/home/user/ashish/FitnessApp/backend/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:443:16)
    at Connection.messageHandler (/home/user/ashish/FitnessApp/backend/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:477:5)
    at Socket.<anonymous> (/home/user/ashish/FitnessApp/backend/node_modules/mongoose/node_modules/mongodb-core/lib/connection/connection.js:321:22)