Add Github Actions for testing

Signed-off-by: Knut Ahlers <knut@ahlers.me>

.github/workflows/test.yaml

@@ -0,0 +1,36 @@
+---
+
+name: test
+on:
+  push:
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        version:
+          - '1.19-alpine'
+          - '1.20-alpine'
+          - alpine
+
+    defaults:
+      run:
+        shell: sh
+
+    container:
+      image: golang:${{ matrix.version }}
+      env:
+        CGO_ENABLED: 0
+        GOPATH: /go
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: go test
+        run: |
+          apk --no-cache add openssl && \
+          go test -v -cover
+
+...