Can't find the example of release_channel for GKE

Terraform
1

Hello,
followed by a rule - there is no stupid questions … frustrated as hell searching and googling…
PLEASE - tell me - how to define the release channel for GKE in terraform!?
all i get is “An argument named “release_channel” is not expected here.”

2

define variable :
variable “release_channel” {
type = string
default = “UNSPECIFIED”
}
use it:
resource “google_container_cluster” “primary” {
name = var.cluster_name
location = var.region
remove_default_node_pool = true
initial_node_count = 1
min_master_version = var.k8s_version
release_channel {
channel = var.release_channel
}