aspnetcore/src/HttpSysServer/samples/HotAddSample/Properties/launchSettings.json

{
  "profiles": {
    "HotAddSample": {
      "commandName": "Project",
      "launchBrowser": true,
      "launchUrl": "http://localhost:12345",
      "environmentVariables": {
        "ASPNETCORE_URLS": "http://localhost:12345",
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}