add release workflow

.github/workflows/release.yml

@@ -0,0 +1,48 @@
+name: Release
+
+on:
+  pull_request:
+    types:
+      - labeled
+      - closed
+
+jobs:
+  release-check:
+    runs-on: ubuntu-latest
+    if: github.event.action == 'labeled'
+    steps:
+      - uses: actions/checkout@v2
+      # Bump version on merging Pull Requests with specific labels.
+      # (bump:major,bump:minor,bump:patch)
+      - uses: haya14busa/action-bumpr@v1
+  pre-release:
+    runs-on: ubuntu-latest
+    if: github.event.action == 'closed' && github.event.pull_request.merged
+    outputs:
+      skip: ${{ steps.bumpr.outputs.skip }}
+    steps:
+      - uses: actions/checkout@v2
+      - id: bumpr
+        uses: haya14busa/action-bumpr@v1
+        with:
+          github_token: ${{ secrets.GH_TOKEN }}
+  release:
+    runs-on: ubuntu-latest
+    if: github.event.action == 'closed' && github.event.pull_request.merged
+    needs: pre-release
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.15
+      - name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@v2
+        if: "!needs.pre-release.outputs.skip"
+        with:
+          version: latest
+          args: release --rm-dist
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}