H-419: run auto-assignment concurrency on PostgreSQL (#77)

Co-authored-by: Rogee <rogee@ipao.vip>

.github/workflows/ci.yml

@@ -31,6 +31,36 @@ jobs:
         working-directory: backend
         run: go vet ./...
 
+  backend-postgres:
+    name: Backend (PostgreSQL concurrency)
+    runs-on: ubuntu-latest
+    services:
+      postgres:
+        image: postgres:16-alpine
+        env:
+          POSTGRES_DB: gochat_test
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd "pg_isready -U postgres -d gochat_test"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 5
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: backend/go.mod
+          cache-dependency-path: backend/go.sum
+      - name: Test auto-assignment concurrency
+        working-directory: backend
+        env:
+          GOCHAT_TEST_DB: postgres
+          GOCHAT_TEST_DB_URL: postgres://postgres:postgres@localhost:5432/gochat_test?sslmode=disable
+        run: go test ./internal/autoassignment -run '^TestAssignmentServiceOnlyOneConcurrentWorkerWinsPostgres$' -count=3
+
   frontend:
     name: Frontend Build
     runs-on: ubuntu-latest