@robpike
I sincerely believe that not having sum types, from day 0, is the biggest sin of Go. Bigger than generics (although the two go well together). But in 2011 it's sad that it didn't include that.

Go also got some things right, like interfaces and having a strong consistent stdlib that relies on them when it makes sense. Formating, integrated tooling, in this it influences every language that has been created since