support Docker container

.github/workflows/verify-on-container.yml

@@ -0,0 +1,28 @@
+# https://help.github.com/en/articles/workflow-syntax-for-github-actions
+
+name: Docker container on Ubuntu 20.04
+
+on:
+- push
+
+jobs:
+  ssh:
+    name: Connect to github.com
+    runs-on: ubuntu-20.04
+    container: ubuntu:20.04
+    steps:
+    - name: Install packages
+      run: |
+        apt update
+        apt -y install openssh-client git
+    - name: Checkout source codes
+      uses: actions/checkout@v2
+    - name: Install SSH key
+      uses: ./.
+      with:
+        key: ${{ secrets.SSH_KEY }}
+        known_hosts: ${{ secrets.KNOWN_HOSTS }}
+    - name: print created files
+      run: ls -l ~/.ssh
+    - name: git clone through SSH
+      run: git clone git@github.com:shimataro/ssh-key-action.git tmp