add script

etc/check_modules.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# check-modules runs "go mod tidy" on each module and exits with a non-zero exit code if there
+# are any module changes. The intent is to confirm that exactly the required
+# modules are declared as dependencies. We should always be able to run "go mod
+# tidy" and expect that no unrelated changes are made to the "go.mod" file.
+set -eu
+
+mods=$(find . -name go.mod)
+for mod in $mods; do
+  pushd $(dirname $mod) > /dev/null
+  echo "Checking $mod..."
+  go mod tidy -v
+  git diff --exit-code go.mod go.sum
+  echo "Checking $mod... done"
+  popd > /dev/null
+done