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Compiling with protoc

Learn to generate Go code with protoc.

Compiling with protoc

A .proto file is turned into code by the protoc compiler and two Go plugins: protoc-gen-go generates messages and protoc-gen-go-grpc generates service interfaces.

go install google.golang.org/protobuf/cmd/protoc-gen-go@latest
go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest

protoc --go_out=. --go_opt=paths=source_relative \
  --go-grpc_out=. --go-grpc_opt=paths=source_relative \
  selam.proto

Output: selam.pb.go and selam_grpc.pb.go.

Don't edit generated code

Generated .pb.go files aren't edited by hand; changes go into the .proto and the code is regenerated. To avoid remembering the command, a directive is added to a source file and go generate ./... is run:

//go:generate protoc --go_out=. --go-grpc_out=. selam.proto

Tools such as Buf also simplify compiling and compatibility checks.

Practice Generated interface

Write a simplified version of the server interface generated by protoc-gen-go-grpc: type SelamlayiciServer interface { Selam(ad string) (string, error) }. Write type sunucu struct{} that satisfies it and check it at compile time with var _ SelamlayiciServer = sunucu{}; then print sunucu{}.Selam("Go").

Starter code

main.go
package main

import "fmt"

func main() {
    // buraya yaz
}

Sample solution

main.go
package main

import "fmt"

type SelamlayiciServer interface {
    Selam(ad string) (string, error)
}

type sunucu struct{}

func (sunucu) Selam(ad string) (string, error) { return "Merhaba " + ad, nil }

var _ SelamlayiciServer = sunucu{}

func main() {
    fmt.Println(sunucu{}.Selam("Go"))
}

Expected output

Merhaba Go <nil>

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which plugin generates the service interfaces (Server/Client)?

  • protoc-gen-go-grpc Correct answer
  • protoc-gen-go
  • go vet
  • gofmt

Explanation: protoc-gen-go generates only message types; client and server code come from protoc-gen-go-grpc.

2 Message output

Question 
protoc ____=. --go-grpc_out=. selam.proto
Answer 
protoc --go_out=. --go-grpc_out=. selam.proto

Explanation: --go_out runs the protoc-gen-go plugin and generates message code.

3 Tool and output

Term Meaning
protoc .proto compiler
protoc-gen-go selam.pb.go
protoc-gen-go-grpc selam_grpc.pb.go
go generate Runs the directives

All lessons in Advanced

1 Reflection

  1. The reflect package
  2. reflect.Type
  3. reflect.Value
  4. Reflecting struct fields
  5. Dynamic call
  6. Summary - Reflection

2 unsafe

  1. The unsafe package
  2. unsafe.Pointer
  3. Sizeof and Alignof
  4. Offsetof
  5. unsafe and slice
  6. Summary - unsafe

3 cgo

  1. What is cgo?
  2. Calling C code
  3. C data types
  4. Go-C conversion
  5. cgo and memory
  6. Summary - cgo

4 plugin

  1. The plugin package
  2. Building a plugin
  3. Loading a plugin
  4. Plugin symbol
  5. Plugin and error
  6. Summary - plugin

5 database/sql

  1. The database/sql package
  2. sql.Open
  3. Query and Exec
  4. Prepared statement
  5. Transaction
  6. Summary - database/sql

6 Middleware

  1. The middleware concept
  2. HTTP middleware
  3. Middleware chain
  4. Logging middleware
  5. Auth middleware
  6. Summary - Middleware

7 gRPC

  1. What is gRPC?
  2. Protobuf definition
  3. Compiling with protoc
  4. gRPC server
  5. gRPC client
  6. Summary - gRPC

8 Project: Microservice

  1. Service skeleton
  2. Database layer
  3. HTTP API
  4. Docker and deployment

9 Docker

  1. Dockerfile
  2. Multi-stage build
  3. scratch image
  4. docker-compose
  5. Build args and labels
  6. Summary - Docker

10 pprof

  1. What is pprof?
  2. CPU profiling
  3. Memory profiling
  4. go test -cpuprofile
  5. The trace tool
  6. Summary - pprof

11 Observability

  1. log/slog
  2. Metrics
  3. Tracing
  4. OpenTelemetry
  5. Health check
  6. Summary - Observability

12 Advanced final

  1. Challenge 1 - Reflection
  2. Challenge 2 - Microservice
  3. Challenge 3 - Performance
  4. Challenge 4 - Database