package main
 
import (
    "errors"
    "fmt"
)
 
var ErrNotFound = errors.New("not found")
 
func fetchData() error {
    return fmt.Errorf("database error: %w", ErrNotFound)
}
 
func main() {
    err := fetchData()
    if err != nil {
        if errors.Is(err, ErrNotFound) {
            fmt.Println("Resource was not found")
        }
        fmt.Println("Original error:", err)
        fmt.Println("Unwrapped error:", errors.Unwrap(err))
    }
}