Update actions and run on both supported Go versions

[skip cd]

.github/workflows/go.yml

@@ -5,13 +5,19 @@ on: [push, pull_request]
 jobs:
   lint:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        go-version: ["1.20", "1.21"]
+
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Set up Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v5
         with:
-          go-version: "1.20"
+          go-version: ${{ matrix.go-version }}
+          cache: true
 
       - name: Install libolm
         run: sudo apt-get install libolm-dev libolm3