Add staticcheck

Only U1000 (unused) yet

.github/workflows/tests-lint.yaml

@@ -31,3 +31,18 @@ jobs:
         test -z "$(git status --porcelain)"
         go vet ./...
         go run dev/envvardoc/envvardoc.go
+
+    - name: Run staticcheck with reviewdog
+      # You may pin to the exact commit or the version.
+      # uses: reviewdog/action-staticcheck@ebb262679ca6a0ab7b43ea94dbcbbc98ae077940
+      uses: reviewdog/action-staticcheck@v1.7.0
+      with:
+        # Reporter of reviewdog command [github-check,github-pr-review].
+        #reporter: # optional, default is github-pr-review
+        #filter_mode: # optional, default is added
+        #fail_on_error: # optional, default is false
+        # Additional reviewdog flags
+        # Target of staticcheck
+        #target: # optional, default is ./...
+        # staticcheck flags
+        staticcheck_flags: '-checks=U1000'  # only unused (yet)