devtools/proxy_worker.sh: die early on bad arg

Change-Id: Ie1a84fd4e161de4cf8256c608c0fe23843511844
Reviewed-on: https://go-review.googlesource.com/c/vulndb/+/401674
Reviewed-by: Julie Qiu <julie@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Jonathan Amsterdam <jba@google.com>

devtools/proxy_worker.sh

@@ -15,4 +15,9 @@ source devtools/lib.sh || { echo "Are you at repo root?"; exit 1; }
 
 env=$1
 
+case $env in
+  dev|prod);;
+  *) die "usage: $0 (dev | prod)"
+esac
+
 cloud-run-proxy -host $(worker_url $env) -token $(impersonation_token $env)