golang 스터디 6주차(함수 고급편 / 에러 핸들링)

go
func fmt.Println(a ...any) (n int, err error)
 
Println formats using the default formats for its operands and writes to standard output. Spaces are always added between operands and a newline is appended. It returns the number of bytes written and any write error encountered.

go
func fmt.Println(a ...any) (n int, err error)
 
Println formats using the default formats for its operands and writes to standard output. Spaces are always added between operands and a newline is appended. It returns the number of bytes written and any write error encountered.

go
func (m UserModel) GetByEmail(email string) (*User, error) {
	query := `
		SELECT id, created_at, name, email, password_hash, activated, version 
		from users
		where email = $1
	`
 
	var user User
 
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
 
	err := m.DB.QueryRowContext(ctx, query, email).Scan(
		&user.ID,
		&user.CreatedAt,
		&user.Name,
		&user.Email,
		&user.Password.hash,
		&user.Activated,
		&user.Version,
	)
 
	if err != nil {
		switch {
		case errors.Is(err, sql.ErrNoRows):
			return nil, ErrRecordNotFound
		default:
			return nil, err
		}
	}
	return &user, nil
}

go
func (m UserModel) GetByEmail(email string) (*User, error) {
	query := `
		SELECT id, created_at, name, email, password_hash, activated, version 
		from users
		where email = $1
	`
 
	var user User
 
	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()
 
	err := m.DB.QueryRowContext(ctx, query, email).Scan(
		&user.ID,
		&user.CreatedAt,
		&user.Name,
		&user.Email,
		&user.Password.hash,
		&user.Activated,
		&user.Version,
	)
 
	if err != nil {
		switch {
		case errors.Is(err, sql.ErrNoRows):
			return nil, ErrRecordNotFound
		default:
			return nil, err
		}
	}
	return &user, nil
}

go
func Sum(a ...int) int {
	var res int
	for _, v := range a {
		res += v
	}
	return res
}
 
func main() {
	f := Sum
 
	fmt.Println(f(10, 20))
}

go
func Sum(a ...int) int {
	var res int
	for _, v := range a {
		res += v
	}
	return res
}
 
func main() {
	f := Sum
 
	fmt.Println(f(10, 20))
}

go
func Hello(f func(...int) int) func(...int) int {
	return f
}
 
func main() {
	f := Sum
 
	fmt.Println(f(10, 20))
	Hello(f)
	}

go
func Hello(f func(...int) int) func(...int) int {
	return f
}
 
func main() {
	f := Sum
 
	fmt.Println(f(10, 20))
	Hello(f)
	}

go
func f() {
	i := 0
	ff := func() {
		i++
	}
	i++
	ff()
}
 
func main() 
	f()
}

go
func f() {
	i := 0
	ff := func() {
		i++
	}
	i++
	ff()
}
 
func main() 
	f()
}

go
type error interface {
	Error() string
}

go
type error interface {
	Error() string
}

go
func panic(v any)
 
The panic built-in function stops normal execution of the current goroutine. When a function F calls panic, normal execution of F stops immediately. Any functions whose execution was deferred by F are run in the usual way, and then F returns to its caller. To the caller G, the invocation of F then behaves like a call to panic, terminating G's execution and running any deferred functions. This continues until all functions in the executing goroutine have stopped, in reverse order. At that point, the program is terminated with a non-zero exit code. This termination sequence is called panicking and can be controlled by the built-in function recover.
Starting in Go 1.21, calling panic with a nil interface value or an untyped nil causes a run-time error (a different panic). The GODEBUG setting panicnil=1 disables the run-time error.

go
func panic(v any)
 
The panic built-in function stops normal execution of the current goroutine. When a function F calls panic, normal execution of F stops immediately. Any functions whose execution was deferred by F are run in the usual way, and then F returns to its caller. To the caller G, the invocation of F then behaves like a call to panic, terminating G's execution and running any deferred functions. This continues until all functions in the executing goroutine have stopped, in reverse order. At that point, the program is terminated with a non-zero exit code. This termination sequence is called panicking and can be controlled by the built-in function recover.
Starting in Go 1.21, calling panic with a nil interface value or an untyped nil causes a run-time error (a different panic). The GODEBUG setting panicnil=1 disables the run-time error.