To disable synchronization context you should call the [ConfigureAwait](<https://msdn.microsoft.com/en-us/library/system.threading.tasks.task.configureawait(v=vs.110).aspx>) method:

async Task() Foo()
{
    await Task.Run(() => Console.WriteLine("Test"));
}

. . .

Foo().ConfigureAwait(false);

ConfigureAwait provides a means to avoid the default SynchronizationContext capturing behavior; passing false for the flowContext parameter prevents the SynchronizationContext from being used to resume execution after the await.

Quote from It’s All About the SynchronizationContext.