Kotlin中使用协程实现异步加载

 //线程代码块
    GlobalScope.launch {
        //异步线程
        val async = async {
            getContactPhone()
        }
        //切换主线程
        withContext(Dispatchers.Main) {
            hello.text = async.await().toString()
            Log.e("MainActivity", async.await().toString()
        }
    }