These logger formatters are meant to be used in the ForSAM softwares, but are leaved open source to allow users of simplelogger to have some examples, and why not inspire from it.
To fix the basics of code format, you can run go fmt.
For a bit more advanced code style checks, you can run golint $(go list ./... | grep -v /vendor/). You'll have to run go get -u golang.org/x/lint/golint before.
File: json_formatter.go
This formatter is used in every services that needs to log in ElasticSearch, through CloudWatch or LogStash.