docker/build-push-action ssh and github secrets private key

build.yml

---
name: build
on:
  workflow_dispatch:
  push:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Set ENV for docker build
        env:
          TOKEN: ${{ secrets.TOKEN }}
        run: |
          mkdir -p ~/.ssh
          echo "$TOKEN" > ~/.ssh/id_rsa
          chmod 600 ~/.ssh/id_rsa
          eval $(ssh-agent -s)
          ssh-add ~/.ssh/id_rsa
          echo "SSH_AUTH_SOCK=$SSH_AUTH_SOCK" >> $GITHUB_ENV
      - uses: docker/build-push-action@v3
        with:
          push: false
          tags: ogwatti/wattitest:latest
          ssh: default

Dockerfile

# syntax = docker/dockerfile:1.0-experimental

FROM node:16-bullseye-slim

ARG ssh_prv_key

RUN apt update \
  && apt upgrade -y \
  && apt install -y git

WORKDIR /app

COPY . .

RUN mkdir -p /root/.ssh && \
    chmod 600 /root/.ssh && \
    ssh-keyscan github.com > /root/.ssh/known_hosts

RUN --mount=type=ssh git clone git@github.com:ogawatti/wattitest-private-repo.git

RUN cat wattitest-private-repo/README.md