different golang error implementation

basic.go

package main

import "errors"
import "fmt"

func bar() error {
	return errors.New("an error")
}

func main() {
	err := bar()
	fmt.Println(err)
}

defining-expected-errors.go

package main

import (
	"errors"
	"fmt"
)

var ErrDivideByZero = errors.New("divide by zero")

func Divide(a, b int) (int, error) {
	if b == 0 {
		return 0, ErrDivideByZero
	}
	return a / b, nil
}

func main() {
	a, b := 5, 0
	result, err := Divide(a, b)
	if err != nil {
		switch {
		case errors.Is(err, ErrDivideByZero):
			fmt.Println("Divide by zero")
		default:
			fmt.Printf("unknown error: %v\n", err)
		}
	}

	fmt.Printf("%d / %d = %d\n", a, b, result)

}

wrap-error.go

package main

import (
	"errors"
	"fmt"
)

var ErrDivideByZero = errors.New("divide by zero")


func doDivide(a, b int) (int, error) {
	result, err := Divide(a, b)
	if err != nil {
		return 0, fmt.Errorf("divide error: %w", err)
	}
	return result, nil

}

func Divide(a, b int) (int, error) {
	if b == 0 {
		return 0, ErrDivideByZero
	}
	return a / b, nil
}

func main() {
	a, b := 5, 0
	result, err := doDivide(a, b)
	if err != nil {
		switch {
		case errors.Is(err, ErrDivideByZero):
			fmt.Println("Divide by zero")
		default:
			fmt.Printf("unknown error: %v\n", err)
		}
	}

	fmt.Printf("%d / %d = %d\n", a, b, result)

}