How to reference count index in another module?

Terraform
1

I have deployed two subnets by using count.index then I need to referece the id of subnet in subnet_route_table_association module. Can any one advise me what is the correct way to do that?

here is my code

/application/demo/main.tf

module “subnet_association” {
source = “…/…/Modules/subnet_association”
subid = var.subid
subnet_id = module.subnet.subnet_id
route_table_id = module.route_table.route_table_id
}

Modules/subnet/main.tf

resource "azurerm_subnet" "module-spoke-subnet" {
  count                                          = var.subnet_count
  name                                           = element(var.subnet_name, count.index)
  resource_group_name                            = var.resource_group_name
  virtual_network_name                           = var.virtual_network_name
  address_prefixes                               = [var.subnet_address[count.index]]
  enforce_private_link_endpoint_network_policies = true
  enforce_private_link_service_network_policies  = true
}
variable "resource_group_name" {
}
variable "virtual_network_name" {
}

Modules/subnet/output.tf

output "subnet_id" {
  value = azurerm_subnet.module-spoke-subnet.*.id
}

Modules/subnet_association/main.tf

resource "azurerm_subnet_route_table_association" "module-subnet-association" {
  subnet_id      = var.subnet_id
  route_table_id = var.route_table_id
}
variable "subnet_id" {

}
variable "route_table_id" {
}

and I`m getting the error

 Error: Incorrect attribute value type
│
│   on ..\..\modules\Subnet_association\main.tf line 20, in resource "azurerm_subnet_route_table_association" "module-subnet-association":
│   20:   subnet_id      = var.subnet_id
│     ├────────────────
│     │ var.subnet_id is tuple with 1 element
│
│ Inappropriate value for attribute "subnet_id": string required.