Book.proto

syntax = "proto3";

option java_multiple_files = true;
option java_package = "com.udaraapi.rpc.book";

package book;

service BookService {
    rpc findAll(Empty) returns (BookMessageList);
    rpc addBook(BookMessage) returns (BookMessage);
}

message BookMessage {
    string title = 1;
    string author = 2;
    string isbn = 3;
    string category = 4;
}

message BookMessageList {
    repeated BookMessage book = 1;
}

message Empty {}

client.go

package main

import (
	"context"
	pb "gogrpc/book"
	"log"

	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial(":6565", grpc.WithInsecure())
	if err != nil {
		log.Fatalf("did not connect: %s", err)
	}
	defer conn.Close()

	client := pb.NewBookServiceClient(conn)

	response, err := client.FindAll(context.Background(), &pb.Empty{})
	log.Printf("Response from server: %v \n", response)
}

server.go

package main

import (
	"context"
	"flag"
	"fmt"
	pb "gogrpc/book"
	"log"
	"net"

	"google.golang.org/grpc"
)

var (
	port = flag.Int("port", 6565, "The server port")
)

type bookServer struct {
	pb.UnimplementedBookServiceServer
	pb.BookMessageList
	pb.BookMessage
}

func (s *bookServer) FindAll(ctx context.Context, empty *pb.Empty) (*pb.BookMessageList, error) {
	var bookMessages = []*pb.BookMessage{
		&pb.BookMessage{
			Title:    "Captain america",
			Author:   "Stan Lee",
			Isbn:     "1234567800",
			Category: "comic",
		},
		&pb.BookMessage{
			Title:    "Iron Man",
			Author:   "Stan Lee",
			Isbn:     "1234567800",
			Category: "comic",
		},
	}

	return &pb.BookMessageList{Book: bookMessages}, nil
}

func (s *bookServer) AddBook(ctx context.Context, bookMessage *pb.BookMessage) (*pb.BookMessage, error) {
	fmt.Println("receive add book")
	return bookMessage, nil
}

func main() {
	flag.Parse()
	lis, err := net.Listen("tcp", fmt.Sprintf("localhost:%d", *port))
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	log.Println("Starting server localhost:", *port)
	server := &bookServer{}
	grpcServer := grpc.NewServer()
	pb.RegisterBookServiceServer(grpcServer, server)
	grpcServer.Serve(lis)
}