Quick start

Prerequisites

Get the example code

The example code is part of the grpc-go repo.

$ git clone -b v1.50.0 --depth 1 https://github.com/grpc/grpc-go

$ cd grpc-go/examples/helloworld

Run the example

examples/helloworld

$ go run greeter_server/main.go

$ go run greeter_client/main.go
Greeting: Hello world

Congratulations! You’ve just run a client-server application with gRPC.

Update the gRPC service

.protoSayHello()HelloRequestHelloReply

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

helloworld/helloworld.protoSayHelloAgain()

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {}
  // Sends another greeting
  rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
  string message = 1;
}

Remember to save the file!

Regenerate gRPC code

.proto

examples/helloworld

$ protoc --go_out=. --go_opt=paths=source_relative \
    --go-grpc_out=. --go-grpc_opt=paths=source_relative \
    helloworld/helloworld.proto

helloworld/helloworld.pb.gohelloworld/helloworld_grpc.pb.go

HelloRequestHelloReply

Update and run the application

You have regenerated server and client code, but you still need to implement and call the new method in the human-written parts of the example application.

Update the server

greeter_server/main.go

func (s *server) SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
        return &pb.HelloReply{Message: "Hello again " + in.GetName()}, nil
}

Update the client

greeter_client/main.gomain()

r, err = c.SayHelloAgain(ctx, &pb.HelloRequest{Name: *name})
if err != nil {
        log.Fatalf("could not greet: %v", err)
}
log.Printf("Greeting: %s", r.GetMessage())

Remember to save your changes.

Run!

examples/helloworld

$ go run greeter_server/main.go

$ go run greeter_client/main.go --name=Alice

Greeting: Hello Alice
Greeting: Hello again Alice

What’s next