Модули, тесты и проект REST API

tasks/
├── go.mod
├── main.go
└── store/
    ├── store.go
    └── store_test.go

module example.com/tasks

go 1.22

package main

import (
	"fmt"
	"strconv"
	"strings"
	"time"
)

func main() {
	fmt.Println(strings.Split("go,java,sql", ","))
	fmt.Println(strings.Repeat("ab", 3), strings.HasPrefix("golang", "go"))
	n, err := strconv.ParseFloat("2.5", 64)
	fmt.Println(n*2, err)
	d := 90 * time.Minute
	fmt.Println(d, d.Hours())
	day := time.Date(2026, time.September, 27, 0, 0, 0, 0, time.UTC)
	fmt.Println(day.Weekday(), day.Format("02.01.2006"))
}

[go java sql]
ababab true
5 <nil>
1h30m0s 1.5
Sunday 27.09.2026

package store

import (
	"errors"
	"strings"
	"sync"
)

var ErrEmptyTitle = errors.New("empty title")

type Task struct {
	ID    int    `json:"id"`
	Title string `json:"title"`
}

type Store struct {
	mu    sync.Mutex
	tasks []Task
}

func (s *Store) Add(title string) (Task, error) {
	title = strings.TrimSpace(title)
	if title == "" {
		return Task{}, ErrEmptyTitle
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	t := Task{ID: len(s.tasks) + 1, Title: title}
	s.tasks = append(s.tasks, t)
	return t, nil
}

func (s *Store) All() []Task {
	s.mu.Lock()
	defer s.mu.Unlock()
	out := make([]Task, len(s.tasks))
	copy(out, s.tasks)
	return out
}

package store

import (
	"errors"
	"testing"
)

func TestAdd(t *testing.T) {
	tests := []struct {
		name    string
		title   string
		want    string
		wantErr error
	}{
		{"simple", "Buy bread", "Buy bread", nil},
		{"trims spaces", "  Learn Go  ", "Learn Go", nil},
		{"empty", "   ", "", ErrEmptyTitle},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			var s Store
			got, err := s.Add(tt.title)
			if !errors.Is(err, tt.wantErr) {
				t.Fatalf("Add(%q) error = %v, want %v", tt.title, err, tt.wantErr)
			}
			if got.Title != tt.want {
				t.Errorf("Add(%q).Title = %q, want %q", tt.title, got.Title, tt.want)
			}
		})
	}
}

$ go test ./...
?   	example.com/tasks	[no test files]
ok  	example.com/tasks/store	0.004s

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"os"

	"example.com/tasks/store"
)

func main() {
	var tasks store.Store
	mux := http.NewServeMux()

	mux.HandleFunc("GET /tasks", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(tasks.All())
	})

	mux.HandleFunc("POST /tasks", func(w http.ResponseWriter, r *http.Request) {
		var in struct {
			Title string `json:"title"`
		}
		if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
			http.Error(w, "invalid JSON", http.StatusBadRequest)
			return
		}
		task, err := tasks.Add(in.Title)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusCreated)
		json.NewEncoder(w).Encode(task)
	})

	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}
	log.Println("listening on :" + port)
	log.Fatal(http.ListenAndServe(":"+port, mux))
}

$ curl -X POST localhost:8080/tasks -d '{"title":"Learn Go"}'
{"id":1,"title":"Learn Go"}
$ curl -X POST localhost:8080/tasks -d '{"title":"   "}'
empty title
$ curl localhost:8080/tasks
[{"id":1,"title":"Learn Go"}]