在CGO上从C ++调用静态var

I have a static var that calls to a constructor in a library in C++, something like this:

class ClassToBuild {
 public:
  ClassToBuild() {
    // Some cool stuff happens here...
  }
};
static ClassToBuild classToBuild;

The problem is that when this file is included in C++, the constructor is being called before the main function, but when I include this libraries from Go, the constructor is not being called. This are third part libraries that I can't modify, and the ClassToBuild is not exposed in the header, so I can't call it from outside.

How can I do to execute the constructor?

Thanks!