--- a/run.go	Wed May 27 10:31:13 2020 +0900
+++ b/run.go	Wed May 27 10:45:45 2020 +0900
@@ -47,7 +47,10 @@
 
 func perform(users []UserInfo) (string, []UserInfo, error) {
 	var entryUsers []UserInfo
-	for _, user := range users {
+	name2Index := make(map[string]int, len(entryUsers))
+
+	for i, user := range users {
+		name2Index[user.Id] = i
 		if user.Done {
 			continue
 		}
@@ -56,22 +59,25 @@
 
 	if len(entryUsers) == 0 {
 		entryUsers = users
-		for _, user := range entryUsers {
-			user.Done = false
+		for i := range entryUsers {
+			entryUsers[i].Done = false
+			users[i].Done = false
 		}
 	}
 
-	targetUser, newUsers := loulette(entryUsers)
+	targetUser := loulette(entryUsers)
+	newUsers := users
+	newUsers[name2Index[targetUser.Id]].Done = true
 
 	return targetUser.Id, newUsers, nil
 }
 
-func loulette(users []UserInfo) (UserInfo, []UserInfo) {
+func loulette(users []UserInfo) UserInfo {
 	rand.Seed(time.Now().UnixNano())
 	index := rand.Intn(len(users))
 	users[index].Done = true
 	for _, user := range users {
 		fmt.Println(user)
 	}
-	return users[index], users
+	return users[index]
 }