Program.cs中配置如下：
//引用Microsoft.Extensions.Configuration;
var Configuration = new ConfigurationBuilder()
.SetBasePath(System.IO.Directory.GetCurrentDirectory())
.AddJsonFile("appsettings.json")
.AddJsonFile("appsettings.test.json", true, reloadOnChange: true).Build();
Console.WriteLine($"Logging:{Configuration["Logging:LogLevel:Default"]}"); //测试读取