[Feature request] Add fields

[hnakamur]

First of all, thanks for creating and sharing a wonderful library!

I think a stack trace with an error message is a big help for debugging, but I also want variable values at the stack where the error occurred. I would like to log those values at the higher stack where I received the error.

So how about adding something like NewWithFields or WrapWithFields?

I implemented a proof of concept at Comparing pkg:a2d6902c6d2a2f194eb3fb474981ab7867c81505...hnakamur:add_fields · pkg/errors

Could you tell me what do you think?
Thanks!

[hnakamur]

I read (Gophercon 2016) Structured Logging and You, in 5 minute and log/log.go at master · aybabtme/log.
Now I think it would be better to use something like github.com/go-kit/kit/log.Context which has ordered key-value pairs.

[davecheney]

Thank you for raising this feature request. I believe this is a duplicate of #34.

I believe I understand what you are asking for, but as I concluded in issue #34 such a feature could not be added without creating a mechanism for state to be passed via a side channel in the error's context.

I do not disagree that this would not be useful, I'm more partial to this idea, moreso than structured logging, but I have decided to not implement this feature at this time as I am concerned that it would be abused.

[hnakamur]

I see. I'm sorry for duplicaton.
Thanks for your explanation.