I have a web server in Golang that connects to Postgres as a StatefulSet. However, I am getting an error with the connection where there is no such host found. The web server was created using ClusterIP as a service for networking and Deployment for creating the pods. Postgres was created using a Headless Service and StatefulSet. The following are my k8s configuration files and also the error message:

# headless-service.yml
apiVersion: v1
kind: Service
metadata:
  name: authentication-headless-service
  labels:
    ims: authentication
spec:
  clusterIP: None # headless service
  selector:
    ims: authentication-postgres
  ports:
    - name: authentication-postgres-h
      port: 5432
      targetPort: 5432

# statefulset.yml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: authentication-postgres-statefulset
spec:
  serviceName: authentication-headless-service
  replicas: 1
  selector:
    matchLabels:
      ims: authentication-postgres
  template:
    metadata:
      labels:
        ims: authentication-postgres
    spec:
      containers:
        - name: postgres
          image: postgres:14.2
          env:
            - name: POSTGRES_USER
              valueFrom:
                secretKeyRef:
                  name: authentication-secret
                  key: POSTGRES_USER
            - name: POSTGRES_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: authentication-secret
                  key: POSTGRES_PASSWORD
            - name: POSTGRES_HOST
              valueFrom:
                secretKeyRef:
                  name: authentication-secret
                  key: POSTGRES_HOST
          ports:
            - containerPort: 5432
              name: postgres
          volumeMounts:
            - name: postgres-authentication-data
              mountPath: /var/lib/postgresql/data
              subPath: postgres # specific to postgres
          livenessProbe:
            tcpSocket:
              port: 5432
            initialDelaySeconds: 60
            periodSeconds: 30
            failureThreshold: 3
          readinessProbe:
            tcpSocket:
              port: 5432
            initialDelaySeconds: 60
            periodSeconds: 30
            failureThreshold: 3
  volumeClaimTemplates:
    - metadata:
        name: postgres-authentication-data
      spec:
        accessModes:
          - "ReadWriteOnce"
        resources:
          requests:
            storage: 500Mi
        storageClassName: ims-storage-class

apiVersion: v1
kind: Secret
metadata:
  name: authentication-secret
type: Opaque
data:
  POSTGRES_USER: YXV0aGVudGljYXRpb24tcG9zdGdyZXM=
  POSTGRES_PASSWORD: cGFzc3dvcmQ=

  # base64 encoded 'authentication-postgres-0.authentication-headless-service.default.svc.cluster.local'
  POSTGRES_HOST: YXV0aGVudGljYXRpb24tcG9zdGdyZXMtMC5hdXRoZW50aWNhdGlvbi1oZWFkbGVzcy1zZXJ2aWNlLmRlZmF1bHQuc3ZjLmNsdXN0ZXIubG9jYWw=

---
apiVersion: v1
kind: Service
metadata:
  name: authentication-clusterip
spec:
  type: ClusterIP
  ports:
    - targetPort: 8001
      port: 8001
  selector:
    ims: authentication

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: authentication-deployment
  namespace: default
spec:
  replicas: 4
  selector:
    matchLabels:
      ims: authentication
  template:
    metadata:
      labels:
        ims: authentication
    spec:
      containers:
        - name: authentication
          image: localhost:5050/ims-authentication:latest
          ports:
            - containerPort: 8001
          env:
            - name: MODE
              value: docker
            - name: POSTGRES_USER
              valueFrom:
                secretKeyRef:
                  name: authentication-secret
                  key: POSTGRES_USER
            - name: POSTGRES_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: authentication-secret
                  key: POSTGRES_PASSWORD
            - name: POSTGRES_HOST
              valueFrom:
                secretKeyRef:
                  name: authentication-secret
                  key: POSTGRES_HOST
            - name: POSTGRES_PORT
              valueFrom:
                configMapKeyRef:
                  name: authentication-configmap
                  key: POSTGRES_PORT
            - name: POSTGRES_DB
              valueFrom:
                configMapKeyRef:
                  name: authentication-configmap
                  key: POSTGRES_DB
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0

This is the error message:

kubectl logs authentication-deployment-99c845645-vr48p

2024/09/18 17:16:10 failed to connect to postgres db: failed to connect to `user=authentication-postgres database=imsdb`: hostname resolving error: lookup authentication-postgres-0.authentication-headless-service.default.svc.cluster.local on 10.96.0.10:53: no such host