But you are lucky if your project has a large group of programmers. There is more probably a large group of projects with a small group of programmers. There are also some large projects: Linux, KDE, LibreOffice, VLC, LLVM, etc... and none is written in Go.
>LibreOffice (based on StarOffice, 6.0 released in 2002)
>VLC (2001)
>LLVM (2003)
I think you have a point r.e there being more smaller projects than large projects with large teams. But this is a terrible argument. Go was released in 2007. Are you being facetious or are you suggesting that porting a mature codebase to Go is that easy? CoreOS was released in 2013 and so was Docker. I know that Docker actually ported to Go after the fact, but it was still relatively young and Go was already mature by then.
This is a weird argument to make, since Go was first introduced in 2009 and the first stable version was released in 2012. All those projects precede Go by a decade or more.
Also, despite Go's short existence, there are already a surprising number of large Go project (Docker, Syncthing, etcd).