[Bug]: Getting "Unable to cache credential: <nil>" when using version 0.6.28

[Kevinbarre]

What happened?

Following my organisation procedure to cache the credentials using aws-iam-authenticator, I was constantly getting the error Unable to cache credential: <nil> after each kubectl command. For instance:

→ ~ kubectl get pods
Cache file /home/kbarre/.kube/cache/aws-iam-authenticator/credentials.yaml does not exist.
No cached credential available.  Refreshing...
Unable to cache credential: <nil>

What you expected to happen?

I was expecting to instead receive the message Updated cached credential

Anything else we need to know?

I tried using the previous version 0.6.27 and it worked correctly with it.

→ ~ kubectl get pods
Cache file /home/kbarre/.kube/cache/aws-iam-authenticator/credentials.yaml does not exist.
No cached credential available.  Refreshing...
Updated cached credential

So I assume there is a regression on latest 0.6.28 version

Installation done by copying the binary aws-iam-authenticator_0.6.28_linux_amd64 from https://github.com/kubernetes-sigs/aws-iam-authenticator/releases/tag/v0.6.28 in /usr/local/bin/

Installation tooling

other (please specify in description)

AWS IAM Authenticator client version

{"Version":"0.6.28","Commit":"2e9e69bd8253b87e08b937d59b1a2b8593942d13"}

Client information

- OS/arch: Ubuntu 22.04.5 LTS x86_64
- kubernetes client & version: kubectl v1.31.0

Kubernetes API Version

Server Version: v1.30.4-eks-a737599

kubeconfig user

[
    {
        "name": "REDACTED",
        "user": {
            "exec": {
                "apiVersion": "client.authentication.k8s.io/v1beta1",
                "args": [
                    "token",
                    "--cache",
                    "--region",
                    "REDACTED",
                    "-i",
                    "REDACTED"
                ],
                "command": "aws-iam-authenticator",
                "env": [
                    {
                        "name": "AWS_PROFILE",
                        "value": "REDACTED"
                    }
                ],
                "interactiveMode": "IfAvailable",
                "provideClusterInfo": false
            }
        }
    }
]

[afinit]

I am also experiencing this problem with v0.6.28 and was able to get around the problem by downgrading to v0.6.27. I also noticed that if i do not set AWS_PROFILE, then it works just fine with the default profile. I'm able to verify that by checking the cached credentials.

I was testing this by running from the command line. The first works, the second errors with the title error

## default profile
aws-iam-authenticator token -i fancy-cluster-id-here --cache

## nondefault profile
EXPORT AWS_PROFILE=nondefault
aws-iam-authenticator token -i fancy-cluster-id-here --cache

Client Information

- OS/arch: MacOS 15.1.1
- kubernetes client & version: kubectl v1.32.0