gofiber/fiber · info

value not found

Error message

value not found

What it means

ErrNotFound is the extractors package sentinel (extractors/extractors.go:65) returned by every leaf extractor when the requested value is absent or empty. It is the expected non-fatal signal used by Chain to fall through to the next extractor, and by application code to short-circuit to a 401/404. Note this is a different value from any fiber-root ErrNotFound.

Solutions

1. Treat ErrNotFound as expected: if errors.Is(err, extractors.ErrNotFound) { return c.SendStatus(fiber.StatusUnauthorized) }.
2. Use Chain so that a missing primary source falls through to a secondary extractor rather than failing the request.
3. Distinguish missing-value (ErrNotFound) from a parse failure (a different error) so error responses stay accurate.

Example fix

// before
val, err := extractor.Extract(c)
if err != nil {
    return err
}
// after
val, err := extractor.Extract(c)
if errors.Is(err, extractors.ErrNotFound) {
    return c.SendStatus(fiber.StatusUnauthorized)
}
if err != nil {
    return err
}

// isExtractorNotFound reports whether the extractor found no value,
// which is an expected condition during chain traversal.
func isExtractorNotFound(err error) bool {
    return errors.Is(err, extractors.ErrNotFound)
}

val, err := extractor.Extract(c)
if err != nil {
    if isExtractorNotFound(err) {
        return c.SendStatus(fiber.StatusUnauthorized)
    }
    return err
}

When it happens

Trigger: FromAuthHeader when the Authorization header is missing or empty; FromCookie when the cookie is unset; FromParam when the URL parameter is empty or fails url.PathUnescape; FromForm/FromHeader/FromQuery when the named field is absent; FromCustom when the supplied function is nil; Chain when no inner extractor yields a value.

Common situations: Building an auth extractor chain (header -> cookie -> query) where some sources are absent in normal traffic; clients that omit a required cookie; routes that share an extractor but not all have the same parameters.

Related errors

• binder: custom binder not found, please be sure to enter…
• binder: invalid destination value
• binder: map destination is nil and cannot be initialized
• binder: map is not convertible to map[string]string or…
• binder: msgpack is not configured, please check docs…

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/8d1ecde6f82d4cd8. Report an issue: GitHub.

Appendix: source

Thrown at extractors/extractors.go:65

	// SourceForm indicates the value is extracted from form data.
	SourceForm

	// SourceQuery indicates the value is extracted from URL query parameters.
	SourceQuery

	// SourceParam indicates the value is extracted from URL path parameters.
	SourceParam

	// SourceCookie indicates the value is extracted from cookies.
	SourceCookie

	// SourceCustom indicates the value is extracted using a custom extractor function.
	SourceCustom
)

// ErrNotFound is returned when the requested value is missing or empty.
var ErrNotFound = errors.New("value not found")

// ErrChainCycle is returned when a chain extractor recursively invokes itself.
var ErrChainCycle = errors.New("cyclic extractor chain")

// Extractor defines a value extraction method with metadata.
type Extractor struct {
	Extract    func(fiber.Ctx) (string, error)
	Key        string      // The parameter/header name used for extraction
	AuthScheme string      // The auth scheme used, e.g., "Bearer"
	Chain      []Extractor // For chained extractors, stores all extractors in the chain
	Source     Source      // The type of source being extracted from
}

// Contains reports whether this extractor, or any extractor in its chain, matches pred.
//
// If pred is nil, Contains returns false.
func (e Extractor) Contains(pred func(Extractor) bool) bool {
	if pred == nil {

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