Getting error:

Publish has encountered an error. Be sure that the Startup.cs for your application is calling AddSwaggerGen from within ConfigureServices in order to generate swagger file.

But startup.cs here is fully loaded:

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers();
    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo { Title = "WeatherForecast API", Version = "v1" });
    });

}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    app.UseSwagger();

    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("v1/swagger.json", "WeatherForecast API V1");
    });
    app.UseHttpsRedirection();

    app.UseRouting();

    app.UseAuthorization();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}