Unpinned resource error when using tflint

[saurabh-khatri-chegg]

module "retool" {
  source  = "git@github.com:tryretool/retool-terraform.git//modules/aws_ecs"
  deployment_name = var.app_name
  launch_type     = "EC2"

  ecs_cluster_name   = var.environment
  ecs_cluster_region = var.region

  workflows_enabled = false
}

TF Lint warning/error:

> TFLint in ./:
> 1 issue(s) found:
> 
> Warning: Module source "git@github.com:tryretool/retool-terraform.git//modules/aws_ecs" is not pinned (terraform_module_pinned_source)