Scale homelab into cloud with Tailscale, Terraform and cloud-init

main.tf

terraform {
  required_providers {
    digitalocean = {
      source = "digitalocean/digitalocean"
    }
  }
}

provider "digitalocean" {
}

variable "tailscale_key" {
  type = "string"
}

resource "digitalocean_vpc" "homelab" {
  name     = "homelab"
  region   = "nyc3"
  ip_range = "10.10.10.0/24"
}

resource "digitalocean_ssh_key" "default" {
  name       = "Labscale - Terraform"
  public_key = file("~/.ssh/id_rsa.pub")
}

resource "digitalocean_droplet" "server" {
  count     = 3
  name      = "server-${count.index}"
  size      = "s-1vcpu-1gb"
  image     = "ubuntu-20-04-x64"
  region    = digitalocean_vpc.homelab.region
  vpc_uuid  = digitalocean_vpc.homelab.id
  ssh_keys  = [digitalocean_ssh_key.default.fingerprint]
  user_data = templatefile("${path.module}/userdata.tpl", {
    tailscale_key = var.tailscale_key
  })
}

resource "digitalocean_project" "labscale" {
  name        = "labscale"
  description = "A project for scaling homelab with tailscale"
  resources   = digitalocean_droplet.server.*.urn
}

output "public_ip" {
  value = digitalocean_droplet.server.*.ipv4_address
}

output "private_ip" {
  value = digitalocean_droplet.server.*.ipv4_address_private 
}

userdata.docker.tpl

#cloud-config
# this variant installs docker as well as tailscale
# using these together you could create a really simple 
# container homelab for quick learning and low cost
---
ssh_pwauth: false
apt:
  sources:
    tailscale.list:
      source: deb https://pkgs.tailscale.com/stable/ubuntu focal main
      keyid: 2596A99EAAB33821893C0A79458CA832957F5868
    docker.list:
      source: deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable
      keyid: 9DC858229FC7DD38854AE2D88D81803C0EBFCD88
packages: 
  - docker-ce
  - docker-ce-cli
  - tailscale
runcmd:
  - tailscale up -authkey ${tailscale_key}

userdata.tpl

#cloud-config
---
apt:
  sources:
    tailscale.list:
      source: deb https://pkgs.tailscale.com/stable/ubuntu focal main
      keyid: 2596A99EAAB33821893C0A79458CA832957F5868
packages: 
  - tailscale
runcmd:
  - [tailscale, up, -authkey, ${tailscale_key}]

@rossedman Thank you for sharing these configs especially with TailScale setup, but this part:

runcmd:
  - [tailscale, up, -authkey, ${tailscale_key}]

unfortunately does not work in my case.

I have posted on Ask Ubuntu two questions(one, two) about this. Maybe you know the solution.