Customizing Swagger Middleware & UI Paths

Program.cs

app.UseSwaggerGen(
       s =>
       {
           //where to serve swagger.json files from
           s.Path = "/PREFIX/swagger/{documentName}/swagger.json";

           //api endpoint server base path customization
           s.PostProcess = (document, request) =>
                           {
                               document.Servers.Clear();
                               document.Servers.Add(
                                   new()
                                   {
                                       Url = $"{request.Scheme}://{request.Host}/PREFIX"
                                   });
                           };
       },
       ui =>
       {
           //where to serve swagger ui from
           ui.Path = "/PREFIX/swagger";

           //where the ui looks for swagger.json files
           ui.DocumentPath = "/PREFIX/swagger/{documentName}/swagger.json";
       });