Error (no exception)
// return multiple results
import (
"fmt"
"errors"
"math"
)
func sqrt (x float64) (float64, error) {
if x < 0 {
return 0, errors.New("Undefined for negative numbers")
}
return math.Sqrt(x), nil
}
func main() {
result, err := sqrt(16)
if err != nil {
fmt.Println(err)
} else {
fmt.Println(result)
}
}Custom Error
As with
fmt.Stringer, the fmt package looks for the error interface when printing values.package main
import (
"fmt"
"time"
)
type MyError struct {
When time.Time
What string
}
func (e *MyError) Error() string {
return fmt.Sprintf("at %v, %s",
e.When, e.What)
}
func run() error {
return &MyError{
time.Now(),
"it didn't work",
}
}
func main() {
if err := run(); err != nil {
fmt.Println(err)
}
}