No other standard library package has json field tags, so there doesn't seem to be any existing precedence to support this.

I don't know if this should actually be done, but if it is, would implementing the TextMarshaler interface (probably which just calls String()) not be a better solution? Then it would work for much more than just JSON--and it wouldn't produce cryptic JSON structs that only make sense in a Go context.

I don't think we want to decide which style of JSON our users which to use for such low-level types.

I think you'll need to write your own wrapper types if you which to serialize these in the JSON style you prefer.

But more generally for this issue, maybe Go needs a policy of when we use JSON struct tags in the standard library and when we don't. https://golang.org/pkg/time/#Time.MarshalJSON seems pretty unoffensive just being a string in a super standard & neutral format. https://golang.org/pkg/math/big/#Int.MarshalJSON also seems basically fine. But that's all we have in the standard library really.

Thank you for the quick comments. Your guys' thoughts and suggestions make absolute sense. I do think it's better to implement the appropriate interfaces so that it doesn't bloat up the standard library.