Problems with the asp core at low load

### Describe the bug
I do not know in what category this issue is. But I recorded bugs.
When the api is written, it should call a server. If the server gets into trouble and runs out. Or slow down. Our service is slow and down.
[link repository code](https://github.com/EngRajabi/sample-httpClient)
Please consider the following tank.
The code that must happen for all requests is 500

requests: :10000
duration: 10s
status codes: {"0":960,"500":70,"503":8970}

### Exceptions (if any)

Loaded result

{"latencies":{"total":30145226477000,"mean":3014522647,"50th":1002607,"90th":15841351701,"95th":30001409856,"99th":30004296027,"max":30025735100,"min":996200},"bytes_in":{"total":2924220,"mean":292.422},"bytes_out":{"total":0,"mean":0},"earliest":"2020-11-17T20:06:34.0727973+03:30","latest":"2020-11-17T20:06:44.0717998+03:30","end":"2020-11-17T20:07:12.2181555+03:30","duration":9999002500,"wait":28146355700,"requests":10000,"rate":1000.0997599510551,"throughput":0,"success":0,"status_codes":{"0":960,"500":70,"503":8970},"errors":["503 Service Unavailable","500 Internal Server Error","Get \"http://localhost:8089/test\": context deadline exceeded (Client.Timeout exceeded while awaiting headers)"]}

### Further technical details
- ASP.NET Core version: 5.0
- Include the output of `dotnet --info`: 5.0 latest
- The IDE (VS / VS Code/ VS4Mac) you're running on, and it's version: Visual Studio latest