github/workflows: add CodeQL workflow

Author: zchee

.github/workflows/codeql.yml

@@ -0,0 +1,55 @@
+name: CodeQL
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+  schedule:
+    - cron: '0 20 * * *'
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-20.04
+
+    strategy:
+      fail-fast: false
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 2
+
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.15.x
+
+    - name: Cache Go module and build cache
+      uses: actions/cache@v2
+      with:
+        key: analyze-go-${{ hashFiles('**/go.mod') }}-${{ hashFiles('**/go.sum') }}
+        path: |
+          ~/go/pkg/mod
+          ~/.cache/go-build
+          ~/Library/Caches/go-build
+          '%LocalAppData%\go-build'
+        restore-keys: |
+          analyze-go-
+
+    - name: Fetch vendors
+      run: |
+        go mod download
+        go mod vendor
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: go
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1