Function Chain

extractors/extractors.go:502–551

Chain creates an Extractor that tries multiple extractors in order until one succeeds. This implements a fallback pattern where multiple extraction sources are attempted in sequence. The function: - Tries each extractor in the order provided - Returns the first successful extraction (non-empty valu

(extractors ...Extractor)

//	Order extractors by security preference. Most secure sources (headers, cookies)
//	should be attempted before less secure ones (query params, form data).
func Chain(extractors ...Extractor) Extractor {
	if len(extractors) == 0 {
		return Extractor{
			Extract: func(fiber.Ctx) (string, error) {
				return "", ErrNotFound
			},
			Source: SourceCustom,
			Key:    "",
			Chain:  []Extractor{},
		}
	}

	// Use the source and key from the first extractor as the primary
	primarySource := extractors[0].Source
	primaryKey := extractors[0].Key
	guardKey := chainGuardKey{id: new(byte)}

	return Extractor{
		Extract: func(c fiber.Ctx) (string, error) {
			if active, ok := c.Locals(guardKey).(bool); ok && active {
				return "", ErrChainCycle
			}

			c.Locals(guardKey, true)
			defer c.Locals(guardKey, false)

			var lastErr error // last error encountered (including ErrNotFound)

			for _, extractor := range extractors {
				if extractor.Extract == nil {
					continue
				}
				v, err := extractor.Extract(c)
				if err == nil && v != "" {
					return v, nil
				}
				if err != nil {
					lastErr = err
				}
			}
			if lastErr != nil {
				return "", lastErr
			}
			return "", ErrNotFound
		},
		Source: primarySource,
		Key:    primaryKey,
		Chain:  append([]Extractor(nil), extractors...), // Defensive copy for introspection
	}
}

// isValidToken68 checks if a string is a valid token68 per RFC 7235/9110.
func isValidToken68(token string) bool {