Add deadcode analysis CI check

Fail the build if any dead code is detected.

.github/workflows/build.yml

@@ -75,6 +75,30 @@ jobs:
             exit 1
           fi
 
+  dead-code-check:
+    name: dead code check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.21'
+
+      - name: Install deadcode tool
+        run: |
+          go install golang.org/x/tools/cmd/deadcode@latest
+
+      - name: Run deadcode analysis
+        run: |
+          deadcode > deadcode-out
+          if [ ! -s deadcode-out ]; then
+            echo "Dead code analysis failed!"
+            echo "Dead code analysis found the following dead code:"
+            cat deadcode-out
+          fi
+
   license-check:
     name: license check
     runs-on: ubuntu-latest