Use await instead of GetAwaiter.GetResult

[darrelmiller]

As the command handler is called asynchronously, we can use async/await instead of GetAwaiter.GetResult. I suspect this may be the source of some deadlocks we are seeing.

OpenAPI.NET/src/Microsoft.OpenApi.Hidi/OpenApiService.cs

Line 109 in 9ce2b27

).ReadAsync(stream).GetAwaiter().GetResult();