Use matrix on actions

[KEINOS]

As shown below, using matrix, we can simplify tests on various Go versions even via container.

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        go: [ '1.14', '1.13' ]
    name: Go ${{ matrix.go }} sample
    steps:
      - uses: actions/checkout@v3
      - name: Setup go
        uses: actions/setup-go@v3
        with:
          go-version: ${{ matrix.go }}
      - run: go run hello.go