A Tour of Go Errors
An error is anything that can describe itself as an error string. The idea is captured by the predefined, built-in interface type, error
, with its single method, Error
, returning a string:
type error interface { Error() string }
The fmt
package's various print routines automatically know to call the method when asked to print an error
.
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) } }