Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpOverrides;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;

namespace swagger_proxy
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            // Register the Swagger generator, defining 1 or more Swagger documents
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
            });
            services.Configure<ForwardedHeadersOptions>(options =>
            {
                //options.KnownProxies.Add(IPAddress.Parse("192.168.56.10"));
                options.ForwardedHeaders =
                     ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto;
            });
        }

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

            app.UseSwagger(c =>
            {
                c.PreSerializeFilters.Add((swagger, httpReq) =>
                {
                    swagger.Servers = new List<OpenApiServer> { new OpenApiServer { Url = $"{httpReq.Scheme}://{httpReq.Host.Value}/{httpReq.Headers["X-Forwarded-Prefix"]}" } };
                });
            });

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

            app.UseAuthorization();

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