for _, k := range keys {
				_, ok := trailers[http.CanonicalHeaderKey(k)]
				if ok {
					return fmt.Errorf("unexpected trailer %s", k)
				}
			}
			return nil
		}
	}
	hasContentLength := func(length int64) checkFunc {
		return func(rec *ResponseRecorder) error {
			if got := rec.Result().ContentLength; got != length {
				return fmt.Errorf("ContentLength = %d; want %d", got, length)
			}

			if cl, err := strconv.ParseUint(clen, 10, 63); err == nil {
				rws.sentContentLen = int64(cl)
			} else {
				clen = ""
			}
		}
		_, hasContentLength := rws.snapHeader["Content-Length"]
		if !hasContentLength && clen == "" && rws.handlerDone && http2bodyAllowedForStatus(rws.status) && (len(p) > 0 || !isHeadResp) {
			clen = strconv.Itoa(len(p))
		}