For_each output not working with GCP

Terraform Providers Google
1

Ideally, I originally wanted to output a list of self_link for GCP in my terraform output, but can’t even get a simple string to work:

module "master-nodes" {
  source          = "./master-nodes"
  network         = google_compute_network.k3s.self_link
  project         = var.project
  service_account = var.service_account
  ssh             = var.ssh

  for_each     = var.servers
  name         = each.key
  subnet_name  = each.key
  region       = each.value.region
  cidr_range   = each.value.cidr_range
  machine_type = each.value.machine_type
}

module "networking" {
  source    = "./networking"
  network   = google_compute_network.k3s.self_link
  instance_names = module.master-nodes.instance_names[*].name
}

I want to feed instance_names into the networking module after the compute resources have been created. Inside my master-nodes modules, I have outputs defined like so:

output "instance_names" {
  value = google_compute_instance.k3s-master.name
  description = "The names of the instances created by the master-nodes module."
}

I’ve tried many variations of this:

output "instance_names" {
  value = [ for compute in google_compute_instance.k3s-master.name: compute.name]
  description = "The names of the instances created by the master-nodes module."
}


output "instance_names" {
  value = [for instance in module.master-nodes : instance.name]
  description = "The names of the instances created by the master-nodes module."
}

Nothing works. How should I set this up?