There are a number of GitHub Actions that exist for working with SHH and SCP. Here’s an example using appleboy/ssh-action and appleboy/scp-action
:

name: Deploy

on: [push]

jobs:
  build:

    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v1

    - name: Copy file via scp
      uses: appleboy/scp-action@master
      env:
        HOST: ${{ secrets.HOST }}
        USERNAME: ${{ secrets.USERNAME }}
        PORT: ${{ secrets.PORT }}
        KEY: ${{ secrets.SSHKEY }}
      with:
        source: "."
        target: "/opt/app"

    - name: Executing remote  command
      uses: appleboy/ssh-action@master
      with:
        host: ${{ secrets.HOST }}
        USERNAME: ${{ secrets.USERNAME }}
        PORT: ${{ secrets.PORT }}
        KEY: ${{ secrets.SSHKEY }}
        script: cat /opt/app/README.md

This copies the git repo to /opt/app on the remote machine. Then, just as an example, it runs a remote command cat /opt/app/README.md

A couple things to note:

• It expects the SSH private key, the Droplet’s IP address, the port being used for SSH (e.g. 22), and the username (e.g. root) to be configured as GitHub secrets.
• I would strongly recommend creating an SSH key specifically for this action/repo rather than re-using an existing one.

Check out the README files for the specific actions for more info.