Support concurrent execution with multiple users

main.go

@@ -24,16 +24,26 @@ type Result struct {
 	IfExistsResult int
 }
 
-func valid_user(username string) int {
+func valid_users(usernames_conn chan string, valid_user_conn chan string) {
+	for username := range usernames_conn {
+		if valid_user(username) != "" {
+			valid_user_conn <- username
+		} else {
+			valid_user_conn <- ""
+		}
+	}
+}
+
+func valid_user(username string) string {
 	request := Request{Username: username}
-	json_request, err := json.Marshal(request)
+	jm, err := json.Marshal(request)
 	if err != nil {
 		panic(err)
 	}
 	response, err := http.Post(
 		ENDPOINT_URL,
 		CONTENT_TYPE,
-		bytes.NewBuffer(json_request),
+		bytes.NewBuffer(jm),
 	)
 	defer response.Body.Close()
 	if err != nil {
@@ -49,28 +59,54 @@ func valid_user(username string) int {
 	if json.Unmarshal(body, &r); err != nil {
 		panic(err)
 	}
-	return r.IfExistsResult
+	if r.IfExistsResult == 0 {
+		return username
+	} else {
+		return ""
+	}
 }
 
 func main() {
 	file := flag.String("f", "", "Specify a file")
 	username := flag.String("u", "", "Specify one username")
 	flag.Parse()
+
 	if *file != "" {
 		f, err := os.Open(*file)
 		if err != nil {
 			panic(err)
 		}
 		defer f.Close()
+
+		var line_count int
+		var usernames []string
+
 		scanner := bufio.NewScanner(f)
 		for scanner.Scan() {
-			username := scanner.Text()
-			if valid_user(username) == 0 {
+			usernames = append(usernames, scanner.Text())
+			line_count += 1
+		}
+
+		usernames_conn := make(chan string, line_count)
+		valid_user := make(chan string)
+		go func() {
+			for _, username := range usernames {
+				usernames_conn <- username
+			}
+		}()
+		for i := 0; i < line_count; i++ {
+			go valid_users(usernames_conn, valid_user)
+		}
+		for i := 0; i < line_count; i++ {
+			username := <-valid_user
+			if username != "" {
 				fmt.Println(username)
 			}
 		}
+		close(usernames_conn)
+		close(valid_user)
 	} else if *username != "" {
-		if valid_user(*username) == 0 {
+		if valid_user(*username) != "" {
 			fmt.Println(*username)
 		}
 	}