diff --git a/main.tf b/main.tf
index 6318396..479e736 100644
--- a/main.tf
+++ b/main.tf
@@ -16,6 +16,7 @@ resource "aws_iam_role" "sns" {
   ]
 }
 EOF
+
 }
 
 # creating policy document and attaching as inline policies instead of using the AutoScalingNotificationAccessRole
@@ -39,8 +40,8 @@ data "aws_iam_policy_document" "auto_scaling_notification_access" {
 
 resource "aws_iam_role_policy" "asg_notification_sns" {
   name   = "${aws_iam_role.sns.name}-asg-notification-policy"
-  role   = "${aws_iam_role.sns.id}"
-  policy = "${data.aws_iam_policy_document.auto_scaling_notification_access.json}"
+  role   = aws_iam_role.sns.id
+  policy = data.aws_iam_policy_document.auto_scaling_notification_access.json
 }
 
 resource "aws_iam_role" "lambda" {
@@ -59,6 +60,7 @@ resource "aws_iam_role" "lambda" {
   ]
 }
 EOF
+
 }
 
 data "aws_iam_policy_document" "lambda" {
@@ -93,14 +95,14 @@ data "aws_iam_policy_document" "lambda" {
 
 resource "aws_iam_role_policy" "lambda" {
   name   = "${aws_iam_role.lambda.name}-policy"
-  role   = "${aws_iam_role.lambda.id}"
-  policy = "${data.aws_iam_policy_document.lambda.json}"
+  role   = aws_iam_role.lambda.id
+  policy = data.aws_iam_policy_document.lambda.json
 }
 
 resource "aws_iam_role_policy" "asg_notification_lambda" {
   name   = "${aws_iam_role.lambda.name}-asg-notification-policy"
-  role   = "${aws_iam_role.lambda.id}"
-  policy = "${data.aws_iam_policy_document.auto_scaling_notification_access.json}"
+  role   = aws_iam_role.lambda.id
+  policy = data.aws_iam_policy_document.auto_scaling_notification_access.json
 }
 
 data "archive_file" "index" {
@@ -110,36 +112,40 @@ data "archive_file" "index" {
 }
 
 resource "aws_lambda_function" "lambda" {
-  runtime       = "python3.6"
-  filename      = "${path.module}/files/index.zip"
-  function_name = "${substr(var.autoscaling_group_name,0,min(64, length(var.autoscaling_group_name)))}"
-  role          = "${aws_iam_role.lambda.arn}"
-  handler       = "index.lambda_handler"
-  timeout       = "${var.function_sleep_time * 2}"
-
-  source_code_hash = "${data.archive_file.index.output_base64sha256}"
+  runtime  = "python3.6"
+  filename = "${path.module}/files/index.zip"
+  function_name = substr(
+    var.autoscaling_group_name,
+    0,
+    min(64, length(var.autoscaling_group_name)),
+  )
+  role    = aws_iam_role.lambda.arn
+  handler = "index.lambda_handler"
+  timeout = var.function_sleep_time * 2
+
+  source_code_hash = data.archive_file.index.output_base64sha256
 
   environment {
     variables = {
-      REGION       = "${var.region}"
-      CLUSTER_NAME = "${var.cluster_name}"
-      SLEEP_TIME   = "${var.function_sleep_time}"
+      REGION       = var.region
+      CLUSTER_NAME = var.cluster_name
+      SLEEP_TIME   = var.function_sleep_time
     }
   }
 
   lifecycle {
     # A workaround when running this code on different machines is to ignore changes, as described here:
     # https://github.com/hashicorp/terraform/issues/7613#issuecomment-241603087
-    ignore_changes = ["filename"]
+    ignore_changes = [filename]
   }
 }
 
 resource "aws_lambda_permission" "sns" {
   statement_id  = "AllowExecutionFromSNS"
-  function_name = "${aws_lambda_function.lambda.arn}"
+  function_name = aws_lambda_function.lambda.arn
   action        = "lambda:InvokeFunction"
   principal     = "sns.amazonaws.com"
-  source_arn    = "${aws_sns_topic.asg_sns.arn}"
+  source_arn    = aws_sns_topic.asg_sns.arn
 }
 
 resource "aws_sns_topic" "asg_sns" {
@@ -147,18 +153,19 @@ resource "aws_sns_topic" "asg_sns" {
 }
 
 resource "aws_sns_topic_subscription" "asg_sns" {
-  topic_arn = "${aws_sns_topic.asg_sns.arn}"
+  topic_arn = aws_sns_topic.asg_sns.arn
   protocol  = "lambda"
-  endpoint  = "${aws_lambda_function.lambda.arn}"
+  endpoint  = aws_lambda_function.lambda.arn
 }
 
 resource "aws_autoscaling_lifecycle_hook" "terminate" {
-  count                   = "${var.lambda_enabled}"
+  count                   = var.lambda_enabled
   name                    = "${var.autoscaling_group_name}-terminate-hook"
-  autoscaling_group_name  = "${var.autoscaling_group_name}"
-  default_result          = "${var.hook_default_result}"
-  heartbeat_timeout       = "${var.hook_heartbeat_timeout}"
+  autoscaling_group_name  = var.autoscaling_group_name
+  default_result          = var.hook_default_result
+  heartbeat_timeout       = var.hook_heartbeat_timeout
   lifecycle_transition    = "autoscaling:EC2_INSTANCE_TERMINATING"
-  notification_target_arn = "${aws_sns_topic.asg_sns.arn}"
-  role_arn                = "${aws_iam_role.sns.arn}"
+  notification_target_arn = aws_sns_topic.asg_sns.arn
+  role_arn                = aws_iam_role.sns.arn
 }
+
diff --git a/variables.tf b/variables.tf
index 235310c..73d878d 100644
--- a/variables.tf
+++ b/variables.tf
@@ -1,16 +1,19 @@
-variable "region" {}
+variable "region" {
+}
 
-variable "cluster_name" {}
+variable "cluster_name" {
+}
 
-variable "autoscaling_group_name" {}
+variable "autoscaling_group_name" {
+}
 
 variable "function_sleep_time" {
   description = "Number of seconds the function should sleep before checking ECS Instance Task Count again"
-  default = 15
+  default     = 15
 }
 
 variable "lambda_enabled" {
-  default = true
+  default = 1
 }
 
 variable "hook_heartbeat_timeout" {
diff --git a/versions.tf b/versions.tf
new file mode 100644
index 0000000..ac97c6a
--- /dev/null
+++ b/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}