I have these locals setup in my terraform.

```
locals {
  subnet_config = {
    config1 = {
      private_subnets = [
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 3, 0),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 3, 1),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 3, 2),
      ]
      public_subnets = [
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 3, 3),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 3, 4),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 3, 5),
      ]
    },
    config2 = {
      private_subnets = [
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 2, 0),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 2, 1),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 2, 2),
      ]
      public_subnets = [
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 5, 24),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 5, 25),
        cidrsubnet("${var.cidr_ip}/${var.cidr_range}", 5, 26),
      ]
    }
  }
}

locals {
  subnet_env = {
    default = local.subnet_config.config1,
    web = local.subnet_config.config2,
  }
}

```

I make reference to the locals above in my terraform vpc module.

```
module "vpc" {
...
  private_subnets     = lookup(local.subnet_env[var.business_unit], "private_subnets", local.subnet_env["default"]["private_subnets"])
  public_subnets      = lookup(local.subnet_env[var.business_unit], "public_subnets", local.subnet_env["default"]["public_subnets"])
...

```

When local.subnet\_env.business\_unit is set to "testthis", I expect local.subnet\_env.default to be picked up but instead i get this.

```
Error: Invalid index

  on .terraform/modules/base/base/vpc.tf line 12, in module "vpc":
  12:   private_subnets     = lookup(local.subnet_env[var.business_unit], "private_subnets", local.subnet_env["default"]["private_subnets"])
    |----------------
    | local.subnet_env is object with 2 attributes
    | var.business_unit is "testthis"

The given key does not identify an element in this collection value.

Error: Invalid index

  on .terraform/modules/base/base/vpc.tf line 13, in module "vpc":
  13:   public_subnets      = lookup(local.subnet_env[var.business_unit], "public_subnets", local.subnet_env["default"]["public_subnets"])
    |----------------
    | local.subnet_env is object with 2 attributes
    | var.business_unit is "testthis"

The given key does not identify an element in this collection value.

```

How Can i get the default value?