Refactoring listener app with configurable fallback (#3096)

cmd/ghalistener/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/actions/actions-runner-controller/cmd/ghalistener/app"
+	"github.com/actions/actions-runner-controller/cmd/ghalistener/config"
+)
+
+func main() {
+	configPath, ok := os.LookupEnv("LISTENER_CONFIG_PATH")
+	if !ok {
+		fmt.Fprintf(os.Stderr, "Error: LISTENER_CONFIG_PATH environment variable is not set\n")
+		os.Exit(1)
+	}
+	config, err := config.Read(configPath)
+	if err != nil {
+		log.Printf("Failed to read config: %v", err)
+		os.Exit(1)
+	}
+
+	app, err := app.New(config)
+	if err != nil {
+		log.Printf("Failed to initialize app: %v", err)
+		os.Exit(1)
+	}
+
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	if err := app.Run(ctx); err != nil {
+		log.Printf("Application returned an error: %v", err)
+		os.Exit(1)
+	}
+}