I am porting a web api 2 service to .net core and I found this line in my old web api service.
ServicePointManager.DefaultConnectionLimit = int.MaxValue;
In ASP.NET 5 apps, use WinHttpHandler.MaxConnectionsPerServer. Its default value is int.MaxValue.
WinHttpHandler.MaxConnectionsPerServer
int.MaxValue
For details, see the .NET Portability Analyzer from the Visual Studio Gallery and WinHttpHandler.MaxConnectionsPerServer on MSDN.