diff --git a/main.tf b/main.tf
index da4142e..a168be2 100644
--- a/main.tf
+++ b/main.tf
@@ -21,25 +21,35 @@
  * ```
  */
 
-provider "azurerm" {}
+provider "azurerm" {
+  version = "~> 2.3"
+  features {
+  }
+}
 
 locals {
-  cluster_name = "${var.name_prefix != "" ? "${var.name_prefix}-${var.cluster_name}" : var.cluster_name}"
+  cluster_name = var.name_prefix != "" ? "${var.name_prefix}-${var.cluster_name}" : var.cluster_name
 }
 
 resource "azurerm_virtual_network" "vnet" {
   name                = "vnet-${local.cluster_name}"
-  address_space       = ["${var.subnet_range}"]
-  location            = "${var.location}"
-  resource_group_name = "${var.resource_group_name}"
+  address_space       = [var.subnet_range]
+  location            = var.location
+  resource_group_name = var.resource_group_name
 
-  tags = "${merge(var.tags, map("Name", var.cluster_name,
-                                "Cluster", var.cluster_name))}"
+  tags = merge(
+    var.tags,
+    {
+      "Name"    = var.cluster_name
+      "Cluster" = var.cluster_name
+    },
+  )
 }
 
 resource "azurerm_subnet" "dcos" {
   name                 = "dcos-${local.cluster_name}"
-  address_prefix       = "${var.subnet_range}"
-  virtual_network_name = "${azurerm_virtual_network.vnet.name}"
-  resource_group_name  = "${var.resource_group_name}"
+  address_prefixes     = [var.subnet_range]
+  virtual_network_name = azurerm_virtual_network.vnet.name
+  resource_group_name  = var.resource_group_name
 }
+
diff --git a/meta.tf b/meta.tf
index 8163051..971e0c4 100644
--- a/meta.tf
+++ b/meta.tf
@@ -1,3 +1,4 @@
 terraform {
-  required_version = "~> 0.11.13"
+  required_version = "~> 0.12"
 }
+
diff --git a/outputs.tf b/outputs.tf
index 130c49f..c59cd89 100644
--- a/outputs.tf
+++ b/outputs.tf
@@ -1,24 +1,24 @@
 output "subnet_id" {
   description = "Subnet ID"
-  value       = "${azurerm_subnet.dcos.id}"
+  value       = azurerm_subnet.dcos.id
 }
 
 output "subnet_name" {
   description = "public subnet name"
-  value       = "${azurerm_subnet.dcos.name}"
+  value       = azurerm_subnet.dcos.name
 }
 
 output "resource_group_name" {
   description = "Name of the azure resource group"
-  value       = "${var.resource_group_name}"
+  value       = var.resource_group_name
 }
 
 output "vnet_id" {
   description = "ID of the VNET"
-  value       = "${azurerm_virtual_network.vnet.id}"
+  value       = azurerm_virtual_network.vnet.id
 }
 
 output "vnet_name" {
   description = "Name of the VNET"
-  value       = "${azurerm_virtual_network.vnet.name}"
-}
+  value       = azurerm_virtual_network.vnet.name
+}
\ No newline at end of file
diff --git a/variables.tf b/variables.tf
index 930a855..78bbebd 100644
--- a/variables.tf
+++ b/variables.tf
@@ -22,6 +22,7 @@ variable "resource_group_name" {
 
 variable "tags" {
   description = "Add custom tags to all resources"
-  type        = "map"
+  type        = map(string)
   default     = {}
 }
+