Get files in a repository using GitHub GraphQL

query.graphql

query { 
  repository(owner: "int128", name: "kubelogin") {
    defaultBranchRef {
      target {
        ... on Commit {
          file(path: "/.github/workflows") {
            type
            object {
              ... on Tree {
                entries {
                  name
                  object {
                    ... on Blob {
                      text
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

result.json

{
  "data": {
    "repository": {
      "defaultBranchRef": {
        "target": {
          "file": {
            "type": "tree",
            "object": {
              "entries": [
                {
                  "name": "golangci-lint.yaml",
                  "object": {
                    "text": "on:\n  push:\n    paths:\n      - .github/workflows/golangci-lint.yaml\n      - '**.go'\njobs:\n  golangci:\n    name: lint\n    runs-on: ubuntu-latest\n    steps:\n      - uses: actions/checkout@v2\n      - uses: golangci/golangci-lint-action@v2\n        with:\n          version: v1.30\n"
                  }
                },
                {
                  "name": "system-test.yaml",
                  "object": {
                    "text": "on:\n  push:\n    paths: \n      - .github/workflows/system-test.yaml\n      - system_test/**\n      - pkg/**\n      - go.*\njobs:\n  system-test:\n    # https://help.github.com/en/actions/automating-your-workflow-with-github-actions/software-installed-on-github-hosted-runners#ubuntu-1804-lts\n    runs-on: ubuntu-18.04\n    steps:\n      - uses: actions/setup-go@v2\n        with:\n          go-version: 1.15\n        id: go\n      - uses: actions/checkout@v2\n      - uses: actions/cache@v2\n        with:\n          path: ~/go/pkg/mod\n          key: go-${{ hashFiles('**/go.sum') }}\n          restore-keys: |\n            go-\n      # https://packages.ubuntu.com/xenial/libnss3-tools\n      - run: sudo apt update\n      - run: sudo apt install -y libnss3-tools\n      - run: mkdir -p ~/.pki/nssdb\n      - run: echo '127.0.0.1 dex-server' | sudo tee -a /etc/hosts\n      - run: make -C system_test -j3\n"
                  }
                }
              ]
            }
          }
        }
      }
    }
  }
}

Thank you for this!
Although, I'd recommend specifying that this query searches for files within the folder .github/workflows and if you'd just want to search for files in the root folder of the repo, then you'd use "/" as the path