Use GCP region_instance_group_manager version block format

* terraform-provider-google v2.19.0 deprecates `instance_template`
within `google_compute_region_instance_group_manager` in order to
support a scheme with multiple version blocks. Adapt our single
version to the new format to resolve deprecation warnings.
* Fixes: Warning: "instance_template": [DEPRECATED] This field
will be replaced by `version.instance_template` in 3.0.0
* Require terraform-provider-google v2.19.0+ (action required)

CHANGES.md

@@ -11,6 +11,12 @@ Notable changes between versions.
 * Replace usage of `template_dir` with `templatefile` function ([#587](https://github.com/poseidon/typhoon/pull/587))
   * Require Terraform version v0.12.6+ (action required)
 
+#### Google
+
+* Use new `google_compute_region_instance_group_manager` version block format
+  * Fixes warning that `instance_template` is deprecated
+  * Require `terraform-provider-google` v2.19.0+ (action required)
+
 ## v1.16.3
 
 * Kubernetes [v1.16.3](https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG-1.16.md#v1163)

google-cloud/container-linux/kubernetes/versions.tf

@@ -3,7 +3,7 @@
 terraform {
   required_version = "~> 0.12.6"
   required_providers {
-    google       = "~> 2.5"
+    google   = "~> 2.19"
     ct       = "~> 0.3"
     template = "~> 2.1"
     null     = "~> 2.1"

google-cloud/container-linux/kubernetes/workers/workers.tf

@@ -5,8 +5,11 @@ resource "google_compute_region_instance_group_manager" "workers" {
 
   # instance name prefix for instances in the group
   base_instance_name = "${var.name}-worker"
-  instance_template  = google_compute_instance_template.worker.self_link
   region             = var.region
+  version {
+    name = "default"
+    instance_template  = google_compute_instance_template.worker.self_link
+  }
 
   target_size  = var.worker_count
   target_pools = [google_compute_target_pool.workers.self_link]