code: func (m *Mrb) GetGlobalVariable(name string) *MrbValue {
  	cs := C.CString(name)
  	defer C.free(unsafe.Pointer(cs))
  	return newValue(m.state, C._go_mrb_gv_get(m.state, C.mrb_intern_cstr(m.state, cs)))
  }
docs: // GetGlobalVariable returns the value of the global variable by the given name.