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Service skeleton

Design the microservice skeleton and layers.

Project: a product service

In this project you will build a small microservice that lists and adds products. The code is split into three layers:

  • handler: reads the HTTP request and writes a JSON response.
  • service: applies business rules (e.g. price can't be negative).
  • repository: stores the data (database or memory).

Each layer uses the one below through an interface, so tests don't need a real database.

Folder layout

A common layout:

urun-servisi/
  cmd/server/main.go     // wires dependencies, starts the server
  internal/urun/model.go // the Urun type
  internal/urun/repo.go  // Repository interface and implementation
  internal/urun/service.go
  internal/urun/handler.go
  go.mod

Packages under internal/ can't be imported from outside the module, which keeps service code private.

Practice Model and interface

Define type Urun struct { ID int; Ad string; Fiyat float64 } and type Repo interface { Ekle(u Urun) error; Liste() []Urun }. In main, print Urun{1, "Kalem", 12.5} with %+v.

Starter code

main.go
package main

import "fmt"

func main() {
    // buraya yaz
}

Sample solution

main.go
package main

import "fmt"

type Urun struct {
    ID    int
    Ad    string
    Fiyat float64
}

type Repo interface {
    Ekle(u Urun) error
    Liste() []Urun
}

func main() {
    fmt.Printf("%+v\n", Urun{1, "Kalem", 12.5})
}

Expected output

{ID:1 Ad:Kalem Fiyat:12.5}

Questions and answers

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

1 Which layer does the rule "price can't be negative" belong to?

  • repository
  • main
  • service Correct answer
  • handler

Explanation: Business rules live in the service layer; the handler only knows HTTP and the repository only storage.

2 Private packages

Question 
urun-servisi/
  ____/urun/service.go
Answer 
urun-servisi/
  internal/urun/service.go

Explanation: The internal folder allows its packages to be imported only from the same module.

3 Layer and role

Term Meaning
handler HTTP and JSON
service Business rules
repository Data storage
cmd/server Wires everything

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