module "foo" {
  # TF-UPGRADE-TODO: In Terraform v0.11 and earlier, it was possible to
  # reference a relative module source without a preceding ./, but it is no
  # longer supported in Terraform v0.12.
  #
  # If the below module source is indeed a relative local path, add ./ to the
  # start of the source string. If that is not the case, then leave it as-is
  # and remove this TODO comment.
  source = "module"
}