标准函数 suspendCoroutine

Kotlin协程标准函数实现：

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suspend fun requestGit() : String {
    return suspendCoroutine<String> { coroutineContext ->
        thread {
            val callFactory: Call.Factory = OkHttpClient()
            val request = Request.Builder()
                .url("https://api.github.com/user")
                .get()
                .build()
            try {
                val call = callFactory.newCall(request)
                val response = call.execute()
                val result = response.body?.string()
                /**
                 * 成功的回调
                 */
                coroutineContext.resume(result ?: "")
            } catch (t: Throwable) {
                /**
                 * 失败的回调
                 */
                coroutineContext.resumeWithException(t)
            }
        }
    }
}

suspend“分饰两角”：声明函数类型时充当async的作用，调用时充当await的作用。