go-kratos/kratos · error

cannot register a nil Codec

Error message

cannot register a nil Codec

What it means

Error "cannot register a nil Codec" thrown in go-kratos/kratos.

Source

Thrown at encoding/encoding.go:27

// methods can be called from concurrent goroutines.
type Codec interface {
	// Marshal returns the wire format of v.
	Marshal(v any) ([]byte, error)
	// Unmarshal parses the wire format into v.
	Unmarshal(data []byte, v any) error
	// Name returns the name of the Codec implementation. The returned string
	// will be used as part of content type in transmission. The result must be
	// static; the result cannot change between calls.
	Name() string
}

var registeredCodecs = make(map[string]Codec)

// RegisterCodec registers the provided Codec for use with all Transport clients and
// servers.
func RegisterCodec(codec Codec) {
	if codec == nil {
		panic("cannot register a nil Codec")
	}
	if codec.Name() == "" {
		panic("cannot register Codec with empty string result for Name()")
	}
	contentSubtype := strings.ToLower(codec.Name())
	registeredCodecs[contentSubtype] = codec
}

// GetCodec gets a registered Codec by content-subtype, or nil if no Codec is
// registered for the content-subtype.
//
// The content-subtype is expected to be lowercase.
func GetCodec(contentSubtype string) Codec {
	return registeredCodecs[contentSubtype]
}

View on GitHub (pinned to 668db92c2c)

When it happens

Trigger: Thrown at encoding/encoding.go:27 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of go-kratos/kratos@668db92c2c (2026-08-16). Data as JSON: /api/errors/e22521a79c99c9f8. Report an issue: GitHub.