Kubernetes envFrom with env

kubernetes-envFrom-env.yml

apiVersion: v1
kind: ConfigMap
metadata:
  name: myconf
data:
  TEST_KEY: my-value
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: mydep
spec:
  replicas: 1
  template:
    spec:
      containers:
      - name: myapp
        image: alpine
        command:
          - sleep
          - '10000'
        envFrom:
          - configMapRef:
              name: myconf
        env:
          - name: GEN_TEST_KEY
            value: 'PREFIX_$(TEST_KEY)'