How to for_each through a list(objects) in Terraform 0.12

I need to deploy a list of GCP compute instances. How do I loop for_each through the "vms" in a list of objects like this:

    "gcp_zone": "us-central1-a",
    "image_name": "centos-cloud/centos-7",
    "vms": [
      {
        "hostname": "test1-srfe",
        "cpu": 1,
        "ram": 4,
        "hdd": 15,
        "log_drive": 300,
        "template": "Template-New",
        "service_types": [
          "sql",
          "db01",
          "db02"
        ]
      },
      {
        "hostname": "test1-second",
        "cpu": 1,
        "ram": 4,
        "hdd": 15,
        "template": "APPs-Template",
        "service_types": [
          "configs"
        ]
      }
    ]    
}

Seem's like I found what to do. If you pass not the maps of maps but the list of maps you can use such code

resource "google_compute_instance" "node" {
    for_each = {for vm in var.vms:  vm.hostname => vm}

    name         = "${each.value.hostname}"
    machine_type = "custom-${each.value.cpu}-${each.value.ram*1024}"
    zone         = "${var.gcp_zone}"

    boot_disk {
        initialize_params {
        image = "${var.image_name}"
        size = "${each.value.hdd}"
        }
    }

    network_interface {
        network = "${var.network}"
    }

    metadata = {
        env_id = "${var.env_id}"
        service_types = "${join(",",each.value.service_types)}"
  }
}

It will create actual number of instance and when you remove for example middle one of three(if you create three:)), terraform will remove what we asked.

From Terraform 0.12, you can use the for_each with modules like the following:

modules/google_compute_instance/variables.tf

variable "hosts" {
    type = map(object({
        hostname        = string
        cpu             = number
        ram             = number
        hdd             = number
        log_drive       = number
        template        = string 
        service_types   = list(string)
      }))
    }

modules/google_compute_instance/main.tf

resource "google_compute_instance" "gcp_instance" {
  for_each = var.hosts

  hostname      = each.value.repository_name
  cpu           = each.value.cpu
  ram           = each.value.ram
  hdd           = each.value.hdd
  log_drive     = each.value.log_drive
  template      = each.value.template
  service_types = each.value.service_types
}

#servers.tf

module "gcp_instances" {
    source = "./modules/google_compute_instance"

    hosts = {
        "test1-srfe" = {
            hostname        = "test1-srfe",
            cpu             = 1,
            ram             = 4,
            hdd             = 15,
            log_drive       = 300,
            template        = "Template-New",
            service_types   = ["sql", "db01", "db02"]
        },
        "test1-second" = {
            hostname        = "test1-second",
            cpu             = 1,
            ram             = 4,
            hdd             = 15,
            log_drive       = 300,
            template        = "APPs-Template",
            service_types   = ["configs"]
        },
    }
}

Of course, you can add as many variables as needed and use them in the module.