code: func GetConfig(L *lua.LState) *Config {
  	const registryKey = "github.com/layeh/gopher-luar"
  
  	registry := L.Get(lua.RegistryIndex).(*lua.LTable)
  	lConfig, ok := registry.RawGetString(registryKey).(*lua.LUserData)
  	if !ok {
  		lConfig = L.NewUserData()
  		lConfig.Value = newConfig()
  		registry.RawSetString(registryKey, lConfig)
  	}
  	return lConfig.Value.(*Config)
  }
docs: // GetConfig returns the luar configuration options for the given *lua.LState.