Authentication Failed when connecting to MongoDB Kubernetes Statefulset - mongodb

Question

I am deploying a mongodb statefulset in Kubernetes and I am setting up my own username and password, but I can't authenticate to the cluster. Please find my YAML manifest below:
Create the Statefulset along with the Headless service
...
apiVersion: v1
kind: Service
metadata:
name: mongo
namespace: ng-mongo
labels:
app: mongo
spec:
ports:
- port: 27017
targetPort: 27017
name: database
clusterIP: None
selector:
role: mongo
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: mongo
namespace: ng-mongo
spec:
serviceName: "mongo"
replicas: 1
selector:
matchLabels:
role: mongo
template:
metadata:
labels:
role: mongo
spec:
containers:
- name: mongo
image: mongo
ports:
- containerPort: 27017
volumeMounts:
- name: mongo-persistent-storage
mountPath: /data/db
env:
- name: MONGO_INITDB_ROOT_USERNAME
value: test
- name: MONGO_INITDB_ROOT_PASSWORD
value: test
- name: MONGO_INITDB_DATABASE
value: ng-db
- name: mongo-sidecar
image: cvallance/mongo-k8s-sidecar
env:
# https://github.com/cvallance/mongo-k8s-sidecar#settings
- name: MONGO_SIDECAR_POD_LABELS
value: "role=mongo"
volumeClaimTemplates:
- metadata:
name: mongo-persistent-storage
spec:
accessModes: [ "ReadWriteOnce" ]
storageClassName: "local-storage"
resources:
requests:
storage: 10Gi
Expose the headless service for testing purposes
kubectl port-forward mongo-0 27017:27017
Try to access the mongodb through mongoshell
mongo -u test -ptest --authenticationDatabase ng-db
And I get the following error:
MongoDB shell version v5.0.11
connecting to: mongodb://127.0.0.1:27017/?authSource=ng-db&compressors=disabled&gssapiServiceName=mongodb
Error: Authentication failed. :
connect#src/mongo/shell/mongo.js:372:17
#(connect):2:6
exception: connect failed
exiting with code 1
Can someone help me on this please? Thank you