Terraform AWS EC2 classic launch in VPC

terraform.tf

# Define VPC id and VPC subnets
variable "vpc_id" {
    default = "vpc-6d408308"
}

variable "vpc_subnets" {
    default = "subnet-fdda6a98,subnet-17914860,subnet-71708228"
}

# Use VPC id for SG
resource "aws_security_group" "consul" {
    vpc_id = "${var.vpc_id}"
}
# Use subnet ids
resource "aws_instance" "consul_server" {
    subnet_id = "${ element(split(",", var.vpc_subnets), count.index) }" # you don't need availability_zone if you have one subnet per AZ
}