net/http.response.clenBuf (field) 2 uses net/http (current package) server.go#L486: clenBuf [10]byte server.go#L1373: setHeader.contentLength = strconv.AppendInt(cw.res.clenBuf[:0], int64(len(p)), 10)
The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)