v := ctx.Value(TraceParamsKey{})
	// Should match SingleHandler.Call checks.
	switch typed := v.(type) {
	case *MSS:
		trace.Path += typed.ToQuery()
	case map[string]string:
		m := MSS(typed)
		trace.Path += m.ToQuery()
	case *URLValues:
		trace.Path += typed.Values().Encode()
	case *NoPayload, *Bytes:
		trace.Path = fmt.Sprintf("%s?payload=%T", trace.Path, typed)
	case string:

// Recycle the underlying map.
func (m *MSS) Recycle() {
	if m != nil && *m != nil {
		mssPool.Put(map[string]string(*m))
		*m = nil
	}
}

// ToQuery constructs a URL query string from the MSS, including "?" if there are any keys.
func (m MSS) ToQuery() string {
	if len(m) == 0 {
		return ""
	}
	var buf strings.Builder
	buf.WriteByte('?')
	keys := make([]string, 0, len(m))
	for k := range m {