default VPC for reference

data_vpc.tf

# lookup for the "default" VPC
data "aws_vpc" "default_vpc" {
  default = true
}

# subnet list in the "default" VPC
# The "default" VPC has all "public subnets"
data "aws_subnet_ids" "default_public" {
  vpc_id = "${data.aws_vpc.default_vpc.id}"
}