support multi-module (#4)

* add multimodule
* re-package modules

error/state.go

@@ -0,0 +1,29 @@
+package error
+
+func NewRaceExinctError(arg ...any) error {
+	return newGenericError(ErrRaceExinct, arg...)
+}
+
+func NewGameNotInitializedError(arg ...any) error {
+	return newGenericError(ErrGameNotInitialized, arg...)
+}
+
+func NewReportNotFoundError(arg ...any) error {
+	return newGenericError(ErrReportNotFound, arg...)
+}
+
+func NewGameStateError(arg ...any) error {
+	return newGenericError(ErrGameStateInvalid, arg...)
+}
+
+func NewDeleteShipTypeExistingGroupError(arg ...any) error {
+	return newGenericError(ErrDeleteShipTypeExistingGroup, arg...)
+}
+
+func NewDeleteShipTypePlanetProductionError(arg ...any) error {
+	return newGenericError(ErrDeleteShipTypePlanetProduction, arg...)
+}
+
+func NewDeleteSciencePlanetProductionError(arg ...any) error {
+	return newGenericError(ErrDeleteSciencePlanetProduction, arg...)
+}