fix: go GitHub workflow cache

Must be specified as deviates from default `messages/message/go.sum` path.

Author: kieran-ryan

.github/workflows/test-go.yml

@@ -39,6 +39,7 @@ jobs:
       uses: actions/setup-go@v6
       with:
         go-version: ${{ matrix.go }}
+        cache-dependency-path: go/go.sum
 
     - name: lint
       working-directory: go