How to put k8 secret in docker cmd argument?

Question

I'm trying to setup the Azure Face recognition container, but wondering how to use a k8 secret as a Docker command "argument."

This works, but I need to replace the ApiKey with my k8 secret.

{
  "kind": "Deployment",
  "spec": {
    "template": {
      "spec": {
        "containers": [
          {
            "name": "azure-face",
            "args": [
              "Eula=accept",
              "Billing=https://microsoft.com",
              "ApiKey=123"
            ]
          }
        ]
      }
    }
  }
}

Create secret like this:

kubectl create secret generic azure-api-key --from-literal=azure-api-key="123"

Tried changing the container args like this but it doesn't work - arugment is not passed as expected: (also tried other variations like ApiKey=${AZURE_API_KEY})

    "containers": [
      {
        "args": [
          "Eula=accept",
          "Billing=https://microsoft.com",
          "ApiKey=$AZURE_API_KEY"
        ],
        "env": [
          {
            "name": "AZURE_API_KEY",
            "valueFrom": {
              "secretKeyRef": {
                "name": "azure-api-key",
                "key": "azure-api-key"
              }
            }
          }
        ]
      }
    ]

Also did docker exec and from inside container verified that:

$ echo $AZURE_API_KEY
$ 123

Answer 1

Looks like this was the issue thanks to @Blokje5:

Note: The environment variable appears in parentheses, "$(VAR)". This is required for the variable to be expanded in the command or args field.

I had tried ${VAR} not $(VAR).