I'm trying to deploy a Go service that uses a Postgres connection on GKE.

The deployment manifest looks like:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: storage-service
  labels:
    app: storage-service
spec:
  selector:
    matchLabels:
      app: storage-service
  template:
    metadata:
      labels:
        app: storage-service
    spec:
      containers:
        - name: app
          image: my-image
          ports:
            - containerPort: 80
          # The following environment variables will contain the database host,
          # user and password to connect to the PostgreSQL instance.
          env:
            - name: SERVICE_DATABASE_NAME
              value: db_storage
            - name: DATABASE_MIGRATIONS_DIR
              value: ./migrations
            - name: MAX_FILE_SIZE
              value: "20000000"
            - name: SERVICE_BASE_PATH
              value: storage
            - name: SERVICE_VERSION
              value: v1
            - name: SERVICE_DESCRIPTION
              value: "A service to store and retrieve files"
            - name: SERVICE_NAME
              value: storage-service
            - name: DATABASE_HOST
              value: 127.0.0.1:3306
            # [START cloudsql_secrets]
            - name: ENV
              valueFrom:
                secretKeyRef:
                  name: environment
                  key: ENV
            - name: PORT
              valueFrom:
                secretKeyRef:
                  name: environment
                  key: DEFAULT_APPLICATION_PORT
            # - name: DATABASE_HOST
            #   valueFrom:
            #     secretKeyRef:
            #       name: sql-proxy
            #       key: DB_HOST
            - name: DATABASE_USER
              valueFrom:
                secretKeyRef:
                  name: sql-proxy
                  key: DB_USER
            - name: DATABASE_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: sql-proxy
                  key: DB_PASS
            - name: DATABASE_SSL_MODE
              valueFrom:
                secretKeyRef:
                  name: sql-proxy
                  key: DB_SSL_MODE
            - name: GCLOUD_PUBLIC_STORAGE_BUCKET
              valueFrom:
                secretKeyRef:
                  name: storage-buckets
                  key: STORAGE_PUBLIC_BUCKET_NAME
            - name: GCLOUD_PRIVATE_STORAGE_BUCKET
              valueFrom:
                secretKeyRef:
                  name: storage-buckets
                  key: STORAGE_PRIVATE_BUCKET_NAME
            # [END cloudsql_secrets]
          volumeMounts:
          - name: firebase-credentials-volume
            mountPath: /storage_service
            readOnly: true
        # Change <INSTANCE_CONNECTION_NAME> here to include your GCP
        # project, the region of your Cloud SQL instance and the name
        # of your Cloud SQL instance. The format is
        # $PROJECT:$REGION:$INSTANCE
        # [START proxy_container]
        - name: cloudsql-proxy
          image: gcr.io/cloudsql-docker/gce-proxy:1.14
          command: ["/cloud_sql_proxy",
                    "-instances=${DB_INSTANCE_CONNECTION_NAME}=tcp:3306",
                    # If running on a VPC, the Cloud SQL proxy can connect via Private IP. See:
                    # https://cloud.google.com/sql/docs/mysql/private-ip for more info.
                    # "-ip_address_types=PRIVATE",
                    "-credential_file=/secrets/cloudsql/credentials.json"]
          # [START cloudsql_security_context]
          securityContext:
            runAsUser: 2  # non-root user
            allowPrivilegeEscalation: false
          # [END cloudsql_security_context]
          env:
            - name: DB_INSTANCE_CONNECTION_NAME
              valueFrom:
                secretKeyRef:
                  name: sql-instance
                  key: DB_INSTANCE_CONNECTION_NAME
          volumeMounts:
            - name: cloudsql-instance-credentials
              mountPath: /secrets/cloudsql
              readOnly: true
        # [END proxy_container]
      # [START volumes]
      volumes:
        - name: cloudsql-instance-credentials
          secret:
            secretName: sql-instance
        - name: firebase-credentials-volume
          secret:
            secretName: firebase
            items:
            - key: firebase_reader.json
              path: firebase.json
      # [END volumes]

When I deploy it to my GKE, we have this logs:

• From sql-proxy container:

> current FDs rlimit set to 1048576, wanted limit is 8500. Nothing to do here.
> using credential file for authentication; email=cloudsql-proxy-reader@corp.iam.gserviceaccount.com
> Listening on 127.0.0.1:3306 for mycorp:europe-west4:ds-db-dev-test05
> Ready for new connections

• App container:

> Dial tcp: lookup 127.0.0.1:3306: no such host

I also put a log to see my postgres connection string:

user=postgres password=PaSS sslmode=disable host=127.0.0.1:3306

And the fact is that my service can't connect with the sql-proxy. Can someone help me?