Note: somewhat duplicate of #1319

What is your suggestion?

When coder server or coder templates create is run (unsure which is best), I suggest displaying an error:

⚠️ Coder's access URL is set to 127.0.0.1 or localhost. Resources provisioned are unlikely to work with Coder.
Please consider changing your `coder server` access URL, or specifying unique access URLs on
templates.

For more information, see: https://github.com/coder/coder/issues/1528

I was chatting with @kylecarbs about this on Discord:

I think the product should block the creation of workspaces when it wouldn't be accessible externally, yup!

Why do you want this feature?

When workspaces are created, the Coder agent on the workspace needs to dial the Coder access URL. If the access url is a loopback address, then the workspace would end up dialing itself instead of the control plane.

Resources will just start and hang on Waiting for connection from dev.

Related: #1345

Are there any workarounds to get this functionality today?

Each example template we provide could include a warning. Templates only leverage resources on the host (e.g docker) can also override the access URL, as done for the docker template in #1507. However, no public cloud templates would work unless Coder is exposed.

Somewhat related: #1176 would allow users to tunnel within Coder itself without the need to use up ngrok, Caddy, or another service to publish and secure a Coder access URL. However, it's a complex undertaking.