ci: adds check to ensure go modules are up to date

Author: poy

.travis.yml

@@ -12,4 +12,5 @@ script:
   - go install github.com/golang/mock/mockgen
   - ./ci/check_go_fmt.sh
   - ./ci/check_go_generate.sh
+  - ./ci/check_go_mod.sh
   - go test -v ./...

ci/check_go_mod.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+# This script is used to ensure that the go.mod file is up to date.
+
+set -euo pipefail
+
+go mod tidy
+
+if [ ! -z "$(git status --porcelain)" ]; then
+    git status
+    echo
+    echo "The go.mod is not up to date."
+    exit 1
+fi