gistfile1.txt

{
  "builders": [
    {
      "image_name": "foo_base_gcp_11_0_{{timestamp}}",
      "account_file": "../gcp_account.json",
      "name": "foo-base-gcp-freebsd11",
      "zone": "us-west1-a",
      "disk_size": "30",
      "source_image": "freebsd-11-0-release-p1-amd64",
      "source_image_project_id": "freebsd-org-cloud-dev",
      "ssh_username": "packer",
      "project_id": "foo-infrastructure",
      "type": "googlecompute"
    }
    ]
}