Add multiple google_project_iam_binding members from previously created service accounts

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1

I have a module that creates a service account and then iam role binding

resource "google_service_account" "sa" {
  account_id   = var.account_id
  display_name = var.account_id
}

resource "google_project_iam_binding" "binding" {
  project = var.project
  role    = var.role

  members = [
    "serviceAccount:${google_service_account.sa.email}",
  ]
}

and then couple of files using that module to create multiple service account with the project like

module "account1-sa" {
  source = ""

  account_id = "account1-sa"
  role       = "roles/some.role"

}

module "account2-sa" {
  source = ""

  account_id = "account2-sa"
  role       = "roles/some.role"
}

and so on.
When I apply this, all the accounts are created but only the last account gets the role assigned, because each one overwrites the previous.
How do I rewrite this, so I can do the binding once but for multiple members which will be accounts created within the same tf project?
Or maybe there is a different/better approach? What I want to achieve is to create couple of service accounts and grant them all the same role.