I am migrating the .Net Project to .Net core 3.1 and there are loads of dependencies in the project so I cannot create a new .Net core application. How can I add Program.Cs file in my existing .Net api project?

I need this code in my existing .Net api project

public class Program
{
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}

    public static IHostBuilder CreateHostBuilder(string\[\] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup();
            })
            .UseSerilog((hostingContext, loggerConfiguration) =>
            {
                var connectionString = hostingContext.Configuration.GetSection("Serilog:WriteTo:0:Args:connectionString");
                connectionString.Value = connectionString.Value;
                loggerConfiguration.ReadFrom.Configuration(hostingContext.Configuration);
            });
}