Using Secrets in environment variables

app.yaml

apiVersion: v1
kind: Secret
metadata:
  name: my-app-secret
type: Opaque
data:
  token: bmxrdnN1NDNwaW5mZXAK
---
apiVersion: v1
kind: Pod
metadata:
  name: my-app
spec:
  containers:
    - name: demo
      image: alpine
      command: ["/bin/ash"]
      args: ["-c", "echo $APP_TOKEN"]
      env:
        - name: APP_TOKEN
          valueFrom:
            secretKeyRef:
              name: my-app-secret
              key: token