support multi-module (#4)

* add multimodule
* re-package modules

server/internal/model/game/state.go

@@ -0,0 +1,16 @@
+package game
+
+import "github.com/google/uuid"
+
+type State struct {
+	ID      uuid.UUID
+	Turn    uint
+	Stage   uint
+	Players []PlayerState
+}
+
+type PlayerState struct {
+	ID      uuid.UUID
+	Name    string
+	Extinct bool
+}