advanced-go-programming-book/examples/ch4-05-grpc-hack/panic-and-log/main.go

package main

import (
	fmt "fmt"
	"log"
	"net"
	"time"

	"golang.org/x/net/context"
	"google.golang.org/grpc"
)

var port = ":5000"

type myGrpcServer struct{}

func (s *myGrpcServer) SayHello(ctx context.Context, in *HelloRequest) (*HelloReply, error) {
	panic("debug")
	return &HelloReply{Message: "Hello " + in.Name}, nil
}

func main() {
	go startServer()
	time.Sleep(time.Second)

	doClientWork()
}

func filter(
	ctx context.Context, req interface{},
	info *grpc.UnaryServerInfo,
	handler grpc.UnaryHandler,
) (resp interface{}, err error) {
	log.Println("fileter:", info)

	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("panic: %v", r)
		}
	}()

	// valiate req

	return handler(ctx, req)
}

func startServer() {
	server := grpc.NewServer(grpc.UnaryInterceptor(filter))
	RegisterGreeterServer(server, new(myGrpcServer))

	lis, err := net.Listen("tcp", port)
	if err != nil {
		log.Panicf("could not list on %s: %s", port, err)
	}

	if err := server.Serve(lis); err != nil {
		log.Panicf("grpc serve error: %s", err)
	}
}

func doClientWork() {
	conn, err := grpc.Dial("localhost"+port, grpc.WithInsecure())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	c := NewGreeterClient(conn)

	r, err := c.SayHello(context.Background(), &HelloRequest{Name: "gopher"})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("doClientWork: %s", r.Message)
}