An argument named "subnets" is not expected here in eks-cluster.tf line 5,

[mklmfane]

This is the result of the command terraform plan launched after I run terraform init -upgrade

Error: Unsupported argument
│
│ on eks-cluster.tf line 5, in module "eks":
│ 5: subnets = module.vpc.private_subnets
│
│ An argument named "subnets" is not expected here.
╵
╷
│ Error: Unsupported argument
│
│ on eks-cluster.tf line 15, in module "eks":
│ 15: workers_group_defaults = {
│
│ An argument named "workers_group_defaults" is not expected here.
╵
╷
│ Error: Unsupported argument
│
│ on eks-cluster.tf line 19, in module "eks":
│ 19: worker_groups = [
│
│ An argument named "worker_groups" is not expected here.

[shakaib-arif]

I have also encountered the same issue a while back and it's related to the eks module version.
It can be fixed by explicitly mentioning the module version in the eks-cluster.tf file as following.

module "eks" {
  source          = "terraform-aws-modules/eks/aws"
  version         = "17.24.0"
  ...

I hope this might help.

Note:

• I did mention to their support about this issue and hopping that they'll fix it soon.
• There is also an open PR someone requested for the same issue's resolution but that involves a bit of code refactoring as well.

[JesseHoch]

Added the module version to both the eks-cluster.tf files in the demo folder and zipped file.