Implement grpc server in the daemon to receive cluster requests

internal/machine/daemon/daemon.go

@@ -3,10 +3,20 @@ package daemon
 import (
 	"context"
 	"fmt"
+	"golang.org/x/sync/errgroup"
+	"google.golang.org/grpc"
+	"log/slog"
+	"net"
 	"uncloud/internal/machine"
+	"uncloud/internal/machine/api"
+	"uncloud/internal/machine/api/pb"
 	"uncloud/internal/machine/network"
 )
 
+const (
+	MachineAPIPort = 51000
+)
+
 func Run(ctx context.Context, dataDir string) error {
 	cfg, err := machine.ParseConfig(machine.ConfigPath(dataDir))
 	if err != nil {
@@ -30,5 +40,38 @@ func Run(ctx context.Context, dataDir string) error {
 	//}
 	//fmt.Println("Addresses:", addrs)
 
-	return wgnet.Run(ctx)
+	addr := fmt.Sprintf("127.0.0.1:%d", MachineAPIPort)
+	listener, err := net.Listen("tcp", addr)
+	if err != nil {
+		return fmt.Errorf("listen API port: %w", err)
+	}
+	grpcServer := grpc.NewServer()
+	pb.RegisterClusterServer(grpcServer, api.NewServer())
+
+	// Use an errgroup to coordinate error handling and graceful shutdown of multiple daemon components.
+	errGroup, ctx := errgroup.WithContext(ctx)
+	errGroup.Go(func() error {
+		slog.Info("Starting API server.", "addr", addr)
+		if sErr := grpcServer.Serve(listener); sErr != nil {
+			return fmt.Errorf("API server failed: %w", sErr)
+		}
+		return nil
+	})
+	errGroup.Go(func() error {
+		if err = wgnet.Run(ctx); err != nil {
+			return fmt.Errorf("WireGuard network failed: %w", err)
+		}
+		return nil
+	})
+	// Shutdown goroutine.
+	errGroup.Go(func() error {
+		<-ctx.Done()
+		slog.Info("Stopping API server.")
+		// TODO: implement timeout for graceful shutdown.
+		grpcServer.GracefulStop()
+		slog.Info("API server stopped.")
+		return nil
+	})
+
+	return errGroup.Wait()
 }