ci(github): switch from CircleCI to GitHub Actions

.github/workflows/ci.yml

@@ -0,0 +1,38 @@
+---
+name: CI
+on: [push]
+
+jobs:
+  build:
+    name: build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-go@v2
+        with:
+          go-version: 1.16
+      - name: Install dependencies
+        run: go mod download
+      - name: Build binary
+        run: make
+      - name: Run and make request
+        run: |
+          ./bin/casecmp --port=8080 &
+          curl --silent --retry 10 --retry-delay 1 --retry-connrefused \
+              http://localhost:8080/
+
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+    needs: [build]
+    if: startsWith(github.ref, 'refs/tags/v')
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-go@v2
+        with:
+          go-version: 1.16
+      - name: goreleaser
+        uses: goreleaser/goreleaser-action@v2
+        with:
+          version: latest
+          args: release --rm-dist