Dynamic IP Restriction for App Services on Azure using terraform

I'm looking for a solution to add multiple ip addresses restriction on the App Service: Below is my code that I'm trying to fix it but I have hard time achieving this:

    variable "ip_address_list" {
  type = list
  default = ["20.20.20.3" , "10.10.10.2"]}

This is just an example of my variable that I want to implement and part of the site_config is the following:

site_config {
  dynamic "ip_restriction" {
for_each = var.ip_address_list
  content {
    ip_address  = cidrhost(ip_restriction.value, 0)
    action                    = "Allow"
  }
}

when I run terraform plan I receive the following error:

on main.tf line 208, in resource "azurerm_app_service" "hook-service":

208: ip_address = cidrhost(ip_restriction.value, 0) ip_restriction.value is "20.20.20.3"

Call to function "cidrhost" failed: invalid CIDR expression: invalid CIDR address: 20.20.20.3.

I received this error for both ip addresses. Also after if there is a way for this solution to be implemented I need to have another restriction based on a virtual subnet which it has to communicate with the other servers that are created in a module

{
      ip_address                = null
      name                      = "Subnet"
      action                    = "Allow"
      virtual_network_subnet_id = azurerm_subnet.subnet.id
      action                    = "Allow"
      priority                  = 200
      service_tag               = null
    }

The subnet have creation of Service Endpoint as ("Microsoft.Web")

cidrhost requires the prefix to be in CIDR notation which is for example

"20.20.20.3/32"

https://www.terraform.io/docs/language/functions/cidrhost.html