Swagger is not generating swagger.json

I was stuck on this problem for hours... and I found the reason...

Check the code below !!

..Startup.cs..

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseHsts();
    }

    app.UseHttpsRedirection();
    app.UseMvc();
    app.UseSwagger(); // if I remove this line, do not work !
    app.UseSwaggerUi3();
}

Just wanted to add my experience here as well. I have given the version in configureServices as V1 (notice the V in caps) and

public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
        services.AddSwaggerGen(c =>
        {
            c.SwaggerDoc("v1", //this v was in caps earlier
            new Swashbuckle.AspNetCore.Swagger.Info
            {
                Version = "v1",//this v was in caps earlier
                Title = "Tiny Blog API",
                Description = "A simple and easy blog which anyone love to blog."
            });
        });
        //Other statements
    }

And then in the configure method it was in small case

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseMvc();
        app.UseSwagger();
        app.UseSwaggerUI(c =>
        {
            c.SwaggerEndpoint("/swagger/v1/swagger.json", "Tiny Blog V1");
        });
    }

May be it can help someone.