Error handling best practices

Core Error Handling
2026-04-17T12:05:42+00:00
Handle errors in Go by explicitly checking return values and using the error interface to manage failures gracefully.

Handle errors explicitly by checking the error return value immediately after a function call and acting on it before proceeding. This pattern prevents silent failures and allows you to log context or recover gracefully.

f, err := os.Open("filename.ext")
if err != nil {
    log.Fatal(err)
}
// proceed with file f

For custom errors, define a type implementing the error interface and use fmt.Errorf to add context:

type NegativeSqrtError float64
func (f NegativeSqrtError) Error() string {
    return fmt.Sprintf("math: square root of negative number %g", float64(f))
}

func Sqrt(f float64) (float64, error) {
    if f < 0 {
        return 0, NegativeSqrtError(f)
    }
    // implementation
}

Use type assertions to inspect specific error types when needed:

if nerr, ok := err.(net.Error); ok && nerr.Temporary() {
    time.Sleep(1e9)
    continue
}
if err != nil {
    log.Fatal(err)
}