update

concurrency/concurrency_v1/chapter1/1_helloworld.cpp

@@ -0,0 +1,20 @@
+//
+// Created by light on 19-11-5.
+//
+
+#include <iostream>
+#include <thread>
+#include <unistd.h>
+
+using namespace std;
+
+void hello() {
+    cout << "hello world" << endl;
+}
+
+int main() {
+    thread t(hello);
+    t.join();       // must add this line otherwise will failed!
+    // 需要注意的是线程对象执行了join后就不再joinable了，所以只能调用join一次。
+    return 0;
+}