通过 appsettings.json 中下面的 serilog 配置解决了

{
  "Serilog": {
    "WriteTo:Sublogger": {
      "Name": "Logger",
      "Args": {
        "configureLogger": {
          "Filter": [
            {
              "Name": "ByIncludingOnly",
              "Args": {
                "expression": "@m like '%unexpected hostname%'"
              }
            }
          ],
          "WriteTo": [
            {
              "Name": "File",
              "Args": {
                "path": "logs/unexpected-hostname-.log",
                "outputTemplate": "{Timestamp:yyyy-MM-dd HH:mm:ss.fff} [{Level}] {Message:l}{NewLine}{RequestPath}{NewLine}{SourceContext}{NewLine}{Exception}",
                "rollingInterval": "Day",
                "retainedFileCountLimit": 7
              }
            }
          ]
        }
      }
    }
  }
}