internal: check ALL modules for go.mod/go.sum misses

Change-Id: I6205846573245d14dc28b1d44dc4c0c1bea459ca
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/46273
Reviewed-by: Noah Dietz <ndietz@google.com>
Reviewed-by: kokoro <noreply+kokoro@google.com>
diff --git a/internal/kokoro/vet.sh b/internal/kokoro/vet.sh
index 22dcaaa..b4d1670 100755
--- a/internal/kokoro/vet.sh
+++ b/internal/kokoro/vet.sh
@@ -36,6 +36,11 @@
 # Fail if a dependency was added without the necessary go.mod/go.sum change
 # being part of the commit.
 go mod tidy
+for i in `find . -name go.mod`; do
+  pushd `dirname $i`;
+    go mod tidy;
+  popd;
+done
 git diff go.mod | tee /dev/stderr | (! read)
 git diff go.sum | tee /dev/stderr | (! read)