Because it works well at various levels and is good at producing low error maintainable code. It's also very stable and has a good stdlib so what's written five

Because it works well at various levels and is good at producing low error maintainable code. It's also very stable and has a good stdlib so what's written five years ago is still working and makes sense. It's not really fun for me (yet?) and I think something like Django is more suitable in many cases, but choosing a core competency go is a pretty safe bet for medium or large company.