FIX and TEST API upgrade from.NET Core 2.1 to .NET 6

Hi, I’m looking good expert who will help me fix some bugs in the API, which occurred after updating the API from .NET Core 2.1 to .NET 6. Write if you have knowledge in .NET filed and do not solve problems only based on stackoverwlow.

Current state: The API returns most of queries, but there is an error with some queries like:

“System.InvalidOperationException: A second operation was started on this context instance before the previous operation was completed. This is usually caused by different threads concurrently using the same DbContext instance. For more information on how to avoid threading problems using DbContext”

It is possible that there are more errors to be discovered, the API should return the values as before the update.