terraform-provider-docker/testdata/resources/docker_container/testAccDockerContainerGroupAddMultipleConfig.tf

resource "docker_image" "foo" {
  name = "nginx:latest"
}

resource "docker_container" "foo" {
  name  = "tf-test"
  image = docker_image.foo.latest

  group_add = [
    1,
    2,
    3,
  ]
}