A working proxy exists.

server/handleprintjob.go

@@ -17,6 +17,8 @@ func handlePrintJob(r *ipp.Request, byteStream io.Reader) *ipp.Response {
 	defer f.Close()
 	io.Copy(f, byteStream)
 	response := ipp.NewResponse(ipp.SuccessfulOk, r.RequestID())
+	response.AddOperatonAttribute(ipp.NewCharSetValue("attributes-charset", "utf-8"))
+	response.AddOperatonAttribute(ipp.NewNaturalLanguage("attributes-natural-language", "en"))
 
 	return response
 }