Technically 2007, but Go 1.0 was in 2009 when the Windows compiler was finally released, Go from 2007 till 2009 was Linux / Unix first. I don't recall when Mac came, but I would not be surprised if very quickly given that GCC worked just fine on Mac at the time.
The Go community made Go work on Windows leading up to 2009, the core maintainers of Go did not make the Windows build themselves, they didn't care about Windows being a target. I say this to emphasize how quickly popular it became that it built up a community that wanted it to build for Windows, and they did.
2013 is when the rest of the world was starting to catch on to Go I suppose, Docker came out in 2013, but I distinctly remember learning Go on Windows in 2009 and building web apps, without any third party packages.
Haha, try 2013. You were not around then ;)
Go 1.0 was released in 2013 (I don't even think the "official date" of March 28, 2012 is correct, or at least, nobody had heard of it).
Apple doing Swift and Google doing Go was basically in response to Node.js
> but I distinctly remember learning Go on Windows in 2009 and building web apps
Very highly doubt it