net/http.response.clenBuf (field) 2 uses net/http (current package) server.go#L477: clenBuf [10]byte server.go#L1293: setHeader.contentLength = strconv.AppendInt(cw.res.clenBuf[:0], int64(len(p)), 10)
The pages are generated with Golds v0.2.8-preview. (GOOS=darwin GOARCH=arm64)