These steps cover writing and running of your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter7/grpc, and navigate to this directory.
2. Run the following command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter7/grpc

You should see a file called go.mod containing the following:

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter7/grpc 

3. Copy tests from ~/projects/go-programming-cookbook-original/chapter7/grpc, or use this as an exercise to write some code of your own!
4. Create a directory called greeter and navigate to it.
5. Create a file called greeter.proto with the following content:

        syntax = "proto3";

        package greeter;

        service GreeterService{
            rpc Greet(GreetRequest) returns (GreetResponse) {}
        }

        message GreetRequest {
            string greeting = 1;
            string name = 2;
        }

        message GreetResponse{
            string response = 1;
        }

6. Navigate back up a directory to grpc.
7. Run the following command:

$ protoc --go_out=plugins=grpc:. greeter/greeter.proto

8. Create a new directory called server and navigate to it.
9. Create a file called greeter.go with the following content. Ensure that you modify the greeter import to use the path you set up in step 3:

        package main

        import (
            "fmt"

            "github.com/PacktPublishing/
             Go-Programming-Cookbook-Second-Edition/
             chapter7/grpc/greeter"
            "golang.org/x/net/context"
        )

        // Greeter implements the interface
        // generated by protoc
        type Greeter struct {
            Exclaim bool
        }

        // Greet implements grpc Greet
        func (g *Greeter) Greet(ctx context.Context, r 
        *greeter.GreetRequest) (*greeter.GreetResponse, error) {
            msg := fmt.Sprintf("%s %s", r.GetGreeting(), r.GetName())
            if g.Exclaim {
                msg += "!"
            } else {
                msg += "."
            }
            return &greeter.GreetResponse{Response: msg}, nil
        }

10. Create a file called server.go with the following content. Ensure that you modify the greeter import to use the path you set up in step 3:

        package main

        import (
            "fmt"
            "net"
 
            "github.com/PacktPublishing/
             Go-Programming-Cookbook-Second-Edition/
             chapter7/grpc/greeter"
            "google.golang.org/grpc"
        )

        func main() {
            grpcServer := grpc.NewServer()
            greeter.RegisterGreeterServiceServer(grpcServer, 
            &Greeter{Exclaim: true})
            lis, err := net.Listen("tcp", ":4444")
            if err != nil {
                panic(err)
            }
            fmt.Println("Listening on port :4444")
            grpcServer.Serve(lis)
        }

11. Navigate back up a directory to grpc.
12. Create a new directory called client and navigate to it.
13. Create a file called client.go with the following content. Ensure that you modify the greeter import to use the path you set up in step 3:

        package main

        import (
            "context"
            "fmt"

            "github.com/PacktPublishing/
             Go-Programming-Cookbook-Second-Edition/
             chapter7/grpc/greeter"
            "google.golang.org/grpc"
        )

        func main() {
            conn, err := grpc.Dial(":4444", grpc.WithInsecure())
            if err != nil {
                panic(err)
            }
            defer conn.Close()

            client := greeter.NewGreeterServiceClient(conn)

            ctx := context.Background()
            req := greeter.GreetRequest{Greeting: "Hello", Name: 
            "Reader"}
            resp, err := client.Greet(ctx, &req)
            if err != nil {
                panic(err)
            }
            fmt.Println(resp)

            req.Greeting = "Goodbye"
            resp, err = client.Greet(ctx, &req)
            if err != nil {
                panic(err)
            }
            fmt.Println(resp)
        }

14. Navigate back up a directory to grpc.

15. Run go run ./server, and you will see the following output:

$ go run ./server
Listening on port :4444

16. In a separate Terminal, run go run ./client from the grpc directory, and you will see the following output:

$ go run ./client
response:"Hello Reader!" 
response:"Goodbye Reader!"

17. The go.mod file may be updated and go.sum file should now be present in the top-level recipe directory.
18. If you copied or wrote your own tests, go up one directory and run go test. Ensure that all the tests pass.