Use in middleware

[Boris M]

Hi,
I want propose add some rollbar in middleware usage for popular packages (gin, echo) and raw go usage. Its will be helpful for new peoples in go.

[Brian O'Rourke]

Hi, thanks for the suggestion. That could be nice documentation but might better belong somewhere else as there are a lot of ways to glue this into different projects and we can't document them all. That said, happy to review patches!