ref: https://github.com/terraform-providers/terraform-provider-aws/pull/12927

main.tf

@@ -60,7 +60,7 @@ resource "aws_security_group" "bastion" {
   }
 
   tags = {
-    Name        = "Bastion"
+    Name = "Bastion"
   }
 
   lifecycle { create_before_destroy = true }
@@ -74,11 +74,11 @@ data "template_file" "userdata" {
 resource "aws_launch_configuration" "bastion" {
   name_prefix = "${format("%s-", "Bastion")}"
 
-  image_id             = "${var.image_id}"
-  instance_type        = "${var.instance_type}"
-  key_name             = "${var.key_name}"
-  security_groups      = ["${aws_security_group.bastion.id}"]
-  user_data            = "${data.template_file.userdata.rendered}"
+  image_id        = "${var.image_id}"
+  instance_type   = "${var.instance_type}"
+  key_name        = "${var.key_name}"
+  security_groups = ["${aws_security_group.bastion.id}"]
+  user_data       = "${data.template_file.userdata.rendered}"
 
   lifecycle {
     create_before_destroy = true
@@ -90,7 +90,6 @@ resource "aws_launch_configuration" "bastion" {
 
 resource "aws_autoscaling_group" "bastion" {
   name                 = "Bastion - ${aws_launch_configuration.bastion.name}"
-  availability_zones   = ["${var.availability_zones}"]
   vpc_zone_identifier  = ["${var.subnet_ids}"]
   launch_configuration = "${aws_launch_configuration.bastion.id}"
   min_size             = "${var.bastion_instances}"
@@ -98,13 +97,13 @@ resource "aws_autoscaling_group" "bastion" {
   desired_capacity     = "${var.bastion_instances}"
 
   tag {
-    key = "Name"
-    value = "Bastion"
+    key                 = "Name"
+    value               = "Bastion"
     propagate_at_launch = true
   }
   tag {
-    key = "service"
-    value = "bastion"
+    key                 = "service"
+    value               = "bastion"
     propagate_at_launch = true
   }
 
@@ -115,5 +114,5 @@ resource "aws_autoscaling_group" "bastion" {
 # Outputs
 #############################################################################################################
 output "security_group" {
-    value = "${aws_security_group.bastion.id}"
+  value = "${aws_security_group.bastion.id}"
 }