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.

Exercise 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.

Show example solution

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})
}

Test yourself

Which layer does the rule "price can't be negative" belong to?
- repository
- main
- service
- handler
Show answer

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

Private packages

urun-servisi/
  ____/urun/service.go

Show answer

urun-servisi/
  internal/urun/service.go

Layer and role

handler

HTTP and JSON
service

Business rules
repository

Data storage
cmd/server

Wires everything

Next lesson: Database layer

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies