Deno "Cannot resolve module ... offline" in CI

Deno needed to download a remote module but the network was unreachable and the module was not in DENO_DIR. In CI this is usually a blocked egress, a proxy, or a cache that was not restored.

What this error means

The run fails with "error: Cannot resolve module \"https://...\"" or "error: Import ... failed: error sending request" when fetching a remote specifier.

deno

error: Import "https://deno.land/std@0.224.0/path/mod.ts" failed: error sending request for url (https://deno.land/std@0.224.0/path/mod.ts): client error (Connect)

Common causes

Blocked or proxied network egress

The runner cannot reach the remote host directly (firewall or required proxy), so the fetch fails.

No restored cache to fall back on

DENO_DIR was not restored, so Deno has no local copy and must reach the network, which is unavailable.

How to fix it

Restore the cache or allow egress

Restore DENO_DIR so remote modules are available offline.
Or configure the proxy the runner needs to reach the host.
Re-run so resolution succeeds.

Terminal

export HTTP_PROXY=http://proxy.internal:3128
export HTTPS_PROXY=http://proxy.internal:3128
deno cache main.ts

Vendor or pre-cache dependencies

Populate DENO_DIR in a network-enabled step, then run the offline step against the restored cache.

.github/workflows/ci.yml

- run: deno cache main.ts
- uses: actions/cache/save@v4
  with:
    path: ~/.cache/deno
    key: deno-${{ hashFiles('deno.lock') }}

How to prevent it

Restore DENO_DIR so remote modules do not need refetching.
Configure required proxies for runners without direct egress.
Pre-cache or vendor dependencies before offline steps.