Fail build if go mod tidy/download changes

.github/workflows/go.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Check out source
         uses: actions/checkout@v2
       - name: Install Linters
-        run: "curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.27.0"
+        run: "curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.28.0"
       - name: Build
         env:
           GO111MODULE: "on"

run_tests.sh

@@ -7,14 +7,28 @@ set -ex
 
 go version
 
+# run `go mod download` and `go mod tidy` and fail if the git status of
+# go.mod and/or go.sum changes
+MOD_STATUS=$(git status --porcelain go.mod go.sum)
+go mod download
+go mod tidy
+UPDATED_MOD_STATUS=$(git status --porcelain go.mod go.sum)
+if [ "$UPDATED_MOD_STATUS" != "$MOD_STATUS" ]; then
+    echo "Running `go mod tidy` modified go.mod and/or go.sum"
+    exit 1
+fi
+
+# run tests
 env GORACE="halt_on_error=1" go test -race ./...
 
+# set output format for linter
 if [[ -v CI ]]; then
     OUT_FORMAT="github-actions"
 else
     OUT_FORMAT="colored-line-number"
 fi
 
+# run linter
 golangci-lint run --disable-all --deadline=10m \
   --out-format=$OUT_FORMAT \
   --enable=gofmt \