Please give me example (code) how to import into main.go a .so file made gccgo?
You can't dynamically load Go "dlls", yet.
Go does not yet support dynamic code loading (i.e. plugins). There are plans to add support in the future, but no set time table at this point:
https://docs.google.com/document/d/1nr-TQHw_er6GOQRsF6T43GGhFDelrAP0NqSS_00RgZQ/preview