I like jq, but jj is so fast it is my go-to for pretty printing large json blobs. Its parsing engine is available as a standalone go module, and I've used it in a few projects where I needed faster parsing than encoding/json:
one way could be you peek method using sth like https://github.com/tidwall/gjson
If you do a lot of JSON parsing for unknown or large structs, you can use gjson: https://github.com/tidwall/gjson
If only parts of a JSON needs to be accessed I can recommend https://github.com/tidwall/gjson.
My problem with serialization in Go isn't so much speed but marshalling/unmarshalling pain.
I've been using these packages with some success:
https://github.com/tidwall/sjson
https://github.com/tidwall/gjson
Not knocking this pkg, just thought I'd share xD