无法创建异步 Main

我正在努力使Main异步，所以我尝试：

class Program
{
    static async Task Main(string[] args)
    {
        Books books = new Books();
        await books.AddBooksAsync();
    }
}

where AddBooksAsync有这样的结构：

public async Task AddBooksAsync()
{
  //some contents
}

我收到此错误：

不包含适合入口点的静态“main”方法

Your visual studio by default will be setted to this Which means that the major version will be 7.0 and not 7.1 you should force it to 7.1 in order to compile it with the 7.1 version

项目属性=>构建=>高级中的第二个选项将语言版本设置为C#最新次要版本（最新）