High CPU usage when decode json string contains numerous '\'

[igotcha]

When json string contains numerous '\' (eg: Windows file path), "decoder.decodeEscapeString" will do too many memory move works.
This is my pprof graph:

And I think the problem is here

[HaoKunT]

I have meet the same problem.

[jamiecuthill]

Also seeing a difference in parsing large JSON blobs with escaped JSON embedded within a string value but only whilst using the Decoder.

As soon as I remove the nested escaped JSON the Decoder performance is much closer to Unmarshal.