update the news fetcher example

examples/concurrent_news_fetcher.v

@@ -1,35 +0,0 @@
-// Please share your thoughts, suggestions, questions, etc here:
-// https://github.com/vlang-io/V/issues/3
-// I'm very interested in your feedback.
-import http
-import json
-import runtime
-
-struct Story {
-        title string
-}
-
-// Fetches top HN stories in 8 coroutines
-fn main() {
-        resp := http.get('https://hacker-news.firebaseio.com/v0/topstories.json')?
-        ids := json.decode([]int, resp.body)?
-        mut cursor := 0
-        for _ in 0..8 {
-                go fn() {
-                        for  {
-                                lock { // Without this lock the program will not compile
-                                        if cursor >= ids.len {
-                                                break
-                                        }
-                                        id := ids[cursor]
-                                        cursor++
-                                }
-                                url := 'https://hacker-news.firebaseio.com/v0/item/$id.json'
-                                resp := http.get(url)?
-                                story := json.decode(Story, resp.body)?
-                                println(story.title)
-                        }
-                }()
-        }
-        runtime.wait() // Waits for all coroutines to finish
-}

examples/news_fetcher.v

@@ -0,0 +1,52 @@
+import http
+import json
+import sync
+import time
+
+const (
+	NR_THREADS = 8
+)
+
+struct Story {
+	title string
+}
+
+struct Fetcher {
+mut:
+	mu     sync.Mutex
+	ids    []int
+	cursor int
+}
+
+fn (f mut Fetcher) fetch() {
+	for {
+		f.mu.lock()
+		if f.cursor >= f.ids.len {
+			return
+		}
+		id := f.ids[f.cursor]
+		f.cursor++
+		f.mu.unlock()
+		resp := http.get('https://hacker-news.firebaseio.com/v0/item/${id}.json')
+		story := json.decode(Story, resp) or {
+			exit('failed to decode a story')
+		}
+		println('#$f.cursor) $story.title')
+	}
+}
+
+// Fetches top HN stories in 8 coroutines
+fn main() {
+	resp := http.get('https://hacker-news.firebaseio.com/v0/topstories.json')
+	ids := json.decode( []int, resp) or {
+		println('failed to fetch topstories.json')
+		return
+	}
+	fetcher := &Fetcher{ids: ids}
+	for i := 0; i < NR_THREADS; i++ {
+		go fetcher.fetch()
+	}
+	println(fetcher.ids)
+	time.sleep(5)
+}
+