How to Properly Await Asynchronous Method Calls in C#'s Main Method?

Calling Async Methods in Main

In C#, it is possible to use asynchronous programming to perform operations in a non-blocking manner. Async methods allow a task to be run concurrently with other code, freeing up the thread to handle other tasks. However, when calling an async method from the Main method, which is not an async method itself, we need to make some adjustments to allow the Main method to wait for the completion of the async operation.

Using Async Main Method (C# 7.1 and Newer)

Starting from C# 7.1, the Main method can be modified to be async, allowing the use of await operator directly. This allows the Main method to act as an entry point for asynchronous operations. For example:

static async Task Main(string[] args)
{
    test t = new test();
    await t.Go();
    Console.WriteLine("finished");
    Console.ReadKey();
}

Using Blocking Wait Method (Earlier C# Versions)

For earlier versions of C#, the Main method cannot be declared as async. Instead, the await operator cannot be used directly. We need to manually wait for the completion of the async operation using the Wait method. For example:

static void Main(string[] args)
{
    test t = new test();
    t.Go().Wait();
    Console.WriteLine("finished");
    Console.ReadKey();
}

Avoiding Deadlock

The example provided in the question attempts to use GetAwaiter.OnCompleted to handle the completion of the Go task. However, this can lead to a deadlock because it tries to run a synchronous continuation on an already synchronized context. By modifying the Main method to be async or using the Wait method as mentioned above, we avoid this issue and allow the async operation to complete properly.

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