我尝试在我的应用程序中的MVVM架构中使用Firebase身份验证。我使用Kotlin和协程，在我的暂停函数中实现Firebase回调后，我遇到了一些与Firebase回调和暂停函数的异步执行相关的概念问题。
我试图通过遵循MVVM架构在Kotlin中实现Google Signin with Firebase。因此，我设计了一个AuthViewModel，它通过调用以下suspend函数将接收到的令牌（从Google One-tap）发送到AuthRepository：

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suspend fun getGoogleSignInResult(token: String): Envelope<AuthUserInfo> {
        return withContext(defaultDispatcher) {
            when(val response = authRemoteDataSource.getGoogleSignInResult(token)) {
                is Envelope.Success -> {
                    Envelope.Success(AuthUserInfo(response.data!!, null))
                }
                else -> {
                    Envelope.Error(response.tag!!, response.message)
                }
            }
        }
    }

此函数，分派到defaultDispatcher并调用我的远程数据源（authRemoteDataSource）中的authRemoteDataSource.getGoogleSignInResult（token）并被挂起。然后authRemoteDataSource获取控件并分派到ioDispatcher，如下所示：

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suspend fun getGoogleSignInResult(token: String): Envelope<FirebaseUser> {
        return withContext(ioDispatcher) {
            // Got an ID token from Google. Use it to authenticate
            // with Firebase.
            var user: FirebaseUser? = null
            val job = launch {
                val firebaseCredential = GoogleAuthProvider.getCredential(token, null)
                auth.signInWithCredential(firebaseCredential)
                    .addOnCompleteListener { task ->
                        if (task.isSuccessful) {
                            // Sign in success, update UI with the signed-in user's information
                            Log.d("TEST", "signInWithCredential:success")
                            user = auth.currentUser
                        } else {
                            // If sign in fails, display a message to the user.
                            
                            Log.w("TEST", "signInWithCredential:failure", task.exception)
                        }
                    }
            }
            job.join() // callbacks are not synchronous so we must wait for the job
            user?.let { Envelope.Success(user!!) }
                ?: Envelope.Error(Envelope.Tag.NON_CACHED_EXCEPTION)
        }
    }

但是这个函数失败了，因为它在分配给addOnCompleteListener的回调完成之前返回;user为NULL，它将返回Envelope.Error（Envelope.Tag.NON_CACHED_EXCEPTION）。似乎对signInWithCredential的调用是异步的，作业没有等待它。问题是：
1.我可以强制Firebase同步执行吗？
顺便说一句，我把上面的代码改成了下面的代码，我希望这也不应该工作：

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suspend fun getGoogleSignInResult(token: String): Envelope<FirebaseUser> {
        var user: FirebaseUser? = null
        val job =  withContext(ioDispatcher) {
            // Got an ID token from Google. Use it to authenticate
            // with Firebase.
            val firebaseCredential = GoogleAuthProvider.getCredential(token, null)
            auth.signInWithCredential(firebaseCredential)
                .addOnCompleteListener { task ->
                    if (task.isSuccessful) {
                        // Sign in success, update UI with the signed-in user's information
                        Log.d("TEST", "signInWithCredential:success")
                        user = auth.currentUser
                    } else {
                        // If sign in fails, display a message to the user.
                        Log.w("TEST", "signInWithCredential:failure", task.exception)
                    }
                }
        }

        // Return
        job.await() // addOnCompleteListener is not synchronous so we must wait for the job
        return user?.let { Envelope.Success(user!!) }
            ?: Envelope.Error(Envelope.Tag.NON_CACHED_EXCEPTION)
    }

但令人惊讶的是，它工作正常;它等待回调addOnCompleteListener完成，然后返回Envelope.Success（user！！）。
2.你知道为什么上面的代码可以正常工作吗？
非常感谢你的帮助。