Injecting environment variables to Postgres pod from Hashicorp Vault - postgresql

Question

I'm trying to set the POSTGRES_PASSWORD, POSTGRES_USER and POSTGRES_DB environment variables in a Kubernetes Pod, running the official postgres docker image, with values injected from Hashicorp Vault.
The issue I experience is that the Postgres Pod will not start and provides no logs as to what might have caused it to stop.
I'm trying to source the injected secrets on startup using args /bin/bash/ source /vault/secrets/backend. Nothing seems to happen once this command is reached. If i add an echo statement in front of source it will display this in the kubectl logs.
Steps taken so far include removing the - args part of configuration and setting the required POSTGRES_PASSWORD variable directly with a test value. When done the pod starts and I can exec into it and verify that the secrets are indeed injected and I'm able to source them. Running cat command on it gives me the following output:
export POSTGRES_PASSWORD="jiasjdi9u2easjdu##djasj#!-d2KDKf"
export POSTGRES_USER="postgres"
export POSTGRES_DB="postgres"
To me this indicates that the Vault injection is working as expected and that this part is configured according to my needs.
*edit: commands after sourcing is indeed run. Tested with echo command
My configuration is as follows:
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: postgres-db
namespace: planet9-demo
labels:
app: postgres-db
environment: development
spec:
serviceName: postgres-service
selector:
matchLabels:
app: postgres-db
replicas: 1
template:
metadata:
annotations:
vault.hashicorp.com/agent-inject: "true"
vault.hashicorp.com/agent-inject-secret-backend: secret/data/backend
vault.hashicorp.com/agent-inject-template-backend: |
{{ with secret "secret/backend/database" -}}
export POSTGRES_PASSWORD="{{ .Data.data.adminpassword}}"
export POSTGRES_USER="{{ .Data.data.postgresadminuser}}"
export POSTGRES_DB="{{ .Data.data.postgresdatabase}}"
{{- end }}
vault.hashicorp.com/role: postgresDB
labels:
app: postgres-db
tier: backend
spec:
containers:
- args:
- /bin/bash
- -c
- source /vault/secrets/backend
name: postgres-db
image: postgres:latest
resources:
requests:
cpu: 300m
memory: 1Gi
limits:
cpu: 400m
memory: 2Gi
volumeMounts:
- name: postgres-pvc
mountPath: /mnt/data
subPath: postgres-data/planet9-demo
env:
- name: PGDATA
value: /mnt/data
restartPolicy: Always
serviceAccount: sa-postgres-db
serviceAccountName: sa-postgres-db
volumes:
- name: postgres-pvc
persistentVolumeClaim:
claimName: postgres-pvc