update Github

.github/workflows/ci.yml

@@ -4,15 +4,15 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.15.x, 1.16.x]
+        go-version: [1.20.x, 1.21.x]
         platform: [ubuntu-latest]
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Install Go
-      uses: actions/setup-go@v2
+      uses: actions/setup-go@v4
       with:
         go-version: ${{ matrix.go-version }}
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
       with:
          path: './src/github.com/kevinburke/nacl'
     # staticcheck needs this for GOPATH