Go Academy · Lesson

Implementing a Unary gRPC Service

Server and client with grpc-go

Lesson 2 of 413 steps

Implementing a Unary gRPC Service is a free Go Academy lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Go Academy learning path, and your progress syncs across the web and the CoddyKit app. The Go Academy course includes 4 lessons in total.

What is a unary RPC?

A unary RPC is the simplest gRPC pattern: the client sends one request and receives one response, similar to a regular function call over the network.

Server implementation

Implement the generated interface. Embed the Unimplemented*Server struct for forward compatibility:

type userServer struct {
    pb.UnimplementedUserServiceServer
    db *sql.DB
}

func (s *userServer) GetUser(ctx context.Context, req *pb.GetUserRequest) (*pb.User, error) {
    // query DB
    return &pb.User{Id: req.Id, Name: "Alice"}, nil
}

Starting the server

Create a gRPC server, register the implementation, and listen on a TCP port:

lis, _ := net.Listen("tcp", ":50051")
grpcSrv := grpc.NewServer()
pb.RegisterUserServiceServer(grpcSrv, &userServer{})
log.Fatal(grpcSrv.Serve(lis))

Client connection

Dial the server and create a client stub:

conn, err := grpc.NewClient("localhost:50051", grpc.WithTransportCredentials(insecure.NewCredentials()))
if err != nil { log.Fatal(err) }
defer conn.Close()
client := pb.NewUserServiceClient(conn)

Making a unary call

Call the RPC method on the client stub as if it were a local function:

ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
user, err := client.GetUser(ctx, &pb.GetUserRequest{Id: 42})
if err != nil { log.Fatalf("error: %v", err) }
fmt.Println(user.Name)

Error handling

gRPC uses status codes. Return errors with status.Errorf and check them with status.Code(err):

import "google.golang.org/grpc/status"
import "google.golang.org/grpc/codes"

// Server:
return nil, status.Errorf(codes.NotFound, "user %d not found", req.Id)
// Client:
if status.Code(err) == codes.NotFound { /* handle */ }

Context propagation

The context passed to the client RPC call carries deadlines and cancellation to the server. The server should pass it to downstream calls (DB, other RPCs).

TLS for production

Replace insecure credentials with TLS in production:

creds, _ := credentials.NewServerTLSFromFile("cert.pem", "key.pem")
grpcSrv := grpc.NewServer(grpc.Creds(creds))

UnimplementedServer

Embedding pb.UnimplementedXxxServer provides stub implementations of all RPC methods that return Unimplemented status. This ensures the server compiles when new RPCs are added to the proto before you implement them.

grpc.Dial vs grpc.NewClient

grpc.Dial is deprecated in newer versions. Use grpc.NewClient which does not establish a connection eagerly but lazily on the first RPC call.

Reflection service

Register the gRPC reflection service to allow tools like grpcurl to introspect available services without the .proto file:

reflection.Register(grpcSrv)

Quick Check

What is the purpose of embedding pb.UnimplementedXxxServer in a gRPC server struct?

Answer it in the interactive lesson

Recap: Unary gRPC

Key points:

Implement generated interface; embed UnimplementedServer
grpc.NewServer() + Register + Serve on TCP listener
Client: grpc.NewClient + generated NewXxxClient
Use status.Errorf/status.Code for gRPC error handling

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Frequently Asked Questions

Is the “Implementing a Unary gRPC Service” lesson free?

Yes — any 3 lessons of the Go Academy learning path, including “Implementing a Unary gRPC Service”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Go Academy course includes 4 lessons in total.

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