I'm attempting to push an image that's built and stored in GitHub Registory to Google Artifact Registry.

The GitHub Actions file contains:

docker build . --tag ghcr.io/myaccount/golang-docker:latest
docker push ghcr.io/myaccount/golang-docker:latest

This obviously builds and pushes it to ghcr.

I want to add an additional step to also push to AR so I've properly setup all the auth stuff in AR and the variables in the actions files:

env:
    IMAGE_NAME: 'golang-docker'
    PROJECT_ID: 'project-blablabla'
    AR_REPO_LOCATION: 'us-west1'
    AR_URL: 'us-west1-docker.pkg.dev/project-blablabla/my-ar-repo'
    SERVICE_ACCOUNT: 'github-actions-service-account@project-blablabla.iam.gserviceaccount.com' 
    WORKLOAD_IDENTITY_PROVIDER: 'projects/123456789/locations/global/workloadIdentityPools/my-app-dev-pool/providers/github-actions-provider'

Then I add

        - name: Google Auth
          id: auth
          uses: 'google-github-actions/auth@v2'
          with:
            token_format: 'access_token'
            project_id: ${{ env.PROJECT_ID }}
            service_account: ${{ env.SERVICE_ACCOUNT }}
            workload_identity_provider: ${{ env.WORKLOAD_IDENTITY_PROVIDER }}
        - name: Docker Auth
          id: docker-auth
          uses: 'docker/login-action@v1'
          with:
            username: 'oauth2accesstoken'
            password: '${{ steps.auth.outputs.access_token }}'
            registry: '${{ env.AR_REPO_LOCATION }}-docker.pkg.dev'    
        - name: Push to AR
          run: |-
            docker push "${{ env.AR_URL }}/${{ env.IMAGE_NAME }}:latest"

But it errors out at the last step with:

An image does not exist locally with the tag: us-west1-docker.pkg.dev/project-blablabla/my-ar-repo/golang-docker
The push refers to repository [us-west1-docker.pkg.dev/platform-blablabla/my-ar-repo/golang-docker]

I'm guessing it has to do with tagging of the image at the build step, but Im' not well versed in docker so I'm not sure what I'm missing. Basically, I'm trying to avoid building the image twice. I want to build it once and then push to one or more registries.

Any ideas?