If I'm going to be burdened by a static type system, then I expect it to do certain things for me in return. One of those things that I take as a given is that a static type system can check that my basic use of types in my program are safe.
Not being able to type-check something as simple as a container lookup is a show-stopper for me because using containers is a huge part of day-to-day programming. Static typing without parametric polymorphism is extremely retrograde -- like Java in the 90's.
I've read rsc's essays on adding parametric polymorphism to Go -- I'm not saying it's a "duh -- just add parametric polymorphism". I'm well aware of the issues -- I'm just saying that Go looks great except for this glaring exception.
