package errors_test
import (
    "fmt"
    "time"
)
// MyError is an error implementation that includes a time and message.
type MyError struct {
    When time.Time
    What string
}
func (e MyError) Error() string {
    return fmt.Sprintf("%v: %v", e.When, e.What)
}
func oops() error {
    return MyError{
        time.Date(1989, 3, 15, 22, 30, 0, 0, time.UTC),
        "the file system has gone away",
    }
}
func Example() {
    if err := oops(); err != nil {
        fmt.Println(err)
    }
    // Output: 1989-03-15 22:30:00 +0000 UTC: the file system has gone away
}

err := errors.New("emit macho dwarf: elf header corrupted")
if err != nil {
    fmt.Print(err)
}

Output:

emit macho dwarf: elf header corrupted

const name, id = "bimmler", 17
err := fmt.Errorf("user %q (id %d) not found", name, id)
if err != nil {
    fmt.Print(err)
}

Output:

user "bimmler" (id 17) not found