Hello everyone. Till today I was using an older version of terraform, but today I upgraded it to the latest available version: ``Terraform v0.12.4

• provider.aws v2.19.0

After that terraform plan is failing with following error:

Error: Invalid template interpolation value

  on eks.tf line 149, in resource "aws_eks_cluster" "xxx-eks":
 149:     subnet_ids = ["${aws_subnet.eks-public.*.id}, ${aws_subnet.eks-private.*.id}"]
    |----------------
    | aws_subnet.eks-public is tuple with 3 elements

Cannot include the given value in a string template: string required.


Error: Invalid template interpolation value

  on eks.tf line 149, in resource "aws_eks_cluster" "xxx-eks":
 149:     subnet_ids = ["${aws_subnet.eks-public.*.id}, ${aws_subnet.eks-private.*.id}"]
    |----------------
    | aws_subnet.eks-private is tuple with 3 elements

Cannot include the given value in a string template: string required.

I can't understand what is going on, moreover that it was working before update. Here you can find piece of code which makes the problem:

resource "aws_eks_cluster" "xxx-eks" {
  name = var.cluster-name
  role_arn = aws_iam_role.eks-cluster.arn
  version = "1.12"

  vpc_config {
    security_group_ids = [aws_security_group.eks-cluster.id]
    subnet_ids = ["${aws_subnet.eks-public.*.id}, ${aws_subnet.eks-private.*.id}"]
  }

  depends_on = [
    aws_iam_role_policy_attachment.GP-cluster-AmazonEKSClusterPolicy,
    aws_iam_role_policy_attachment.GP-cluster-AmazonEKSServicePolicy,
  ]
}

Please help me to solve this issue.

Hi @apparentlymart . Thank you very much. You solved my day.