Go Best Practice

ctx.go

func (u *User) Store(ctx context.Context) error {
        ...
        if err := u.Hash.Store(ctx, k, u); err != nil {
                return err
        }
        ...
}

ctx_cancel_main.go

func main() {
        ctx, cancel := context.WithCancel(context.Background())
        defer cancel()
  
        go func() {
                sigchan := make(chan os.Signal, 1)
                signal.Notify(sigchan, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM)
                <-sigchan
                cancel()
        }()
  
        svr := &ctxpkg.Server{}
        svr.Run(ctx) // ← long running process
        log.Println("graceful stop")
}

ctx_cancel_svr.go

type Server struct{}

func (s *Server) Run(ctx context.Context) {
        for {
                select {
                case <-ctx.Done():
                        log.Println("cancel received, attempting graceful stop...")
                        // clean up process
                        return
                default:
                        handleRequest()
                }
        }
}

func handleRequest() {
        time.Sleep(time.Duration(rand.Intn(10)) * time.Second)
}

ctx_timeout_main.go

func main() {
        ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
        defer cancel() // ← cancel should be called even if timeout didn't happen

        SendRequest(ctx) // ← subroutine that can get stuck
}

ctx_timeout_req.go

func SendRequest(ctx context.Context) {
        respCh := make(chan interface{}, 1)
        go sendRequest(respCh)

        select {
        case <-ctx.Done():
                log.Println("operation timed out!")
        case <-respCh:
                log.Println("response received")
        }
}

func sendRequest(ch chan<- interface{}) {
        time.Sleep(60 * time.Second)
        ch <- struct{}{}
}

ctx_value_handler.go

var logCtxKey = &struct{}{}

func handleRequest(w http.ResponseWriter, r *http.Request) {
        method, path := r.Method, r.URL.Path
        logger := log.With().
                Str("method", method).
                Str("path", path).
                Logger()
        ctxWithLogger := context.WithValue(r.Context(), logCtxKey, logger)
        ...
        accessDatabase(ctxWithLogger)
}

ctx_value_subroutine.go

func accessDatabase(ctx context.Context) {
        logger := ctx.Value(logCtxKey).(zerolog.Logger)
        logger.Debug().Msg("accessing database")
}

pkg_iface.go

package bestpractice

type User struct {}

type UserService interface {
        User(context.Context, string) (*User, error)
}

pkg_redis.go

package redis

import (
        "github.com/thirdfort/go-bestpractice"
        "github.com/thirdfort/go-redis"
)

type UserService struct {
        ...
}

func (s *UserService) User(ctx context.Context, id string) (*bestpractice.User, error) {
        ...
        err := redis.RetrieveHash(ctx, k)
        ...
}

pkg_repetition.go

package user

func GetUser(ctx context.Context, id string) (*User, error) {
        ...
}

tdt.go

type Restaurant struct {
	openAt  time.Time
	closeAt time.Time
}

func (r Restaurant) IsOpen(at time.Time) bool {
	return (at.Equal(r.openAt) || at.After(r.openAt)) &&
		(at.Equal(r.closeAt) || at.Before(r.closeAt))
}

tdt_before_open_test.go

func TestRestaurantBeforeOpen(t *testing.T) {
	r := Restaurant{
		openAt:  time.Date(2022, time.January, 17, 12, 0, 0, 0, time.UTC),
		closeAt: time.Date(2022, time.January, 17, 22, 0, 0, 0, time.UTC),
	}
	
	input := r.openAt.Add(-1 * time.Second)
	got := r.IsOpen(input)
	assert.False(t, got)
}

func TestRestaurantBeforeClose(t *testing.T) {
	r := Restaurant{
		openAt:  time.Date(2022, time.January, 17, 12, 0, 0, 0, time.UTC),
		closeAt: time.Date(2022, time.January, 17, 22, 0, 0, 0, time.UTC),
	}

	input := r.closeAt
	got := r.IsOpen(input)
	assert.True(t, got)
}

tdt_just_opened_test.go

func TestRestaurantJustOpened(t *testing.T) {
	r := Restaurant{
		openAt:  time.Date(2022, time.January, 17, 12, 0, 0, 0, time.UTC),
		closeAt: time.Date(2022, time.January, 17, 22, 0, 0, 0, time.UTC),
	}

	input := r.openAt
	got := r.IsOpen(input)
	assert.True(t, got)
}

tdt_test.go

func TestRestaurantTableDriven(t *testing.T) {
	r := Restaurant{
		openAt:  time.Date(2022, time.January, 17, 12, 0, 0, 0, time.UTC),
		closeAt: time.Date(2022, time.January, 17, 22, 0, 0, 0, time.UTC),
	}

	// test cases
	cases := map[string]struct {
		input time.Time
		want  bool
	}{
		"before open": {
			input: r.openAt.Add(-1 * time.Second),
			want:  false,
		},
		"just opened": {
			input: r.openAt,
			want:  true,
		},
		"before close": {
			input: r.closeAt,
			want:  true,
		},
		"just closed": {
			input: r.closeAt.Add(1 * time.Second),
			want:  false,
		},
	}

	for name, c := range cases {
		t.Run(name, func(t *testing.T) {
			got := r.IsOpen(c.input)
			assert.Equal(t, c.want, got)
		})
	}
}