install apidiff with 'go install'

Author: pohly

.github/workflows/test.yml

@@ -31,7 +31,7 @@ jobs:
       - name: Add GOBIN to PATH
         run: echo "PATH=$(go env GOPATH)/bin:$PATH" >>$GITHUB_ENV
       - name: Install dependencies
-        run: GO111MODULE=off go get golang.org/x/exp/cmd/apidiff
+        run: go install golang.org/x/exp/cmd/apidiff@latest
       - name: Checkout old code
         uses: actions/checkout@v4
         with: