tracing

type RegistryRequest struct {
	Ctx      context.Context
	Endpoint string
	Options  registry.PluginOp
}

type Request interface{}

type Span interface{}

type Tracing interface {
	ServerBegin(operationName string, r Request) Span
	ServerEnd(span Span, code int, message string)
	ClientBegin(operationName string, r Request) Span
	ClientEnd(span Span, code int, message string)
}