ci: add GitHub Actions workflow for container IP setup

- Add a new GitHub Actions workflow for container IP example
- Configure the workflow to run on push events
- Set up a job to run on the latest Ubuntu with a Golang container
- Enable IPv6 in the container
- Add steps to check out the repository, set up Docker, and retrieve the container's IP address
- Set the container IP as an environment variable and use it in a subsequent step

Signed-off-by: appleboy <[email protected]>

.github/workflows/ipv6.yaml

@@ -0,0 +1,29 @@
+name: Container IP Example
+
+on: [push]
+
+jobs:
+  testing:
+    runs-on: ubuntu-latest
+    container:
+      image: golang:1.21-alpine
+      options: --sysctl net.ipv6.conf.all.disable_ipv6=0
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker
+        run: |
+          # Get the container ID of the current container
+          CONTAINER_ID=$(cat /proc/self/cgroup | grep 'docker' | sed 's/^.*\///' | tail -n 1)
+          echo "Container ID: $CONTAINER_ID"
+
+          # Get the container IP address using docker inspect
+          CONTAINER_IP=$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $CONTAINER_ID)
+          echo "Container IP: $CONTAINER_IP"
+
+          # Set the container IP as an environment variable
+          echo "CONTAINER_IP=$CONTAINER_IP" >> $GITHUB_ENV
+
+      - name: Use Container IP
+        run: echo "The container IP is ${{ env.CONTAINER_IP }}"