Use JWT (Authorization: Bearer) in Swagger in ASP.NET Core

I struggled with the same problem and found a working solution in this blogpost:
http://blog.sluijsveld.com/28/01/2016/CustomSwaggerUIField

It comes down to adding this in your configurationoptions

services.ConfigureSwaggerGen(options =>
{
   options.OperationFilter<AuthorizationHeaderParameterOperationFilter>();
});

and the code for the operationfilter

public class AuthorizationHeaderParameterOperationFilter : IOperationFilter
{
   public void Apply(Operation operation, OperationFilterContext context)
   {
      var filterPipeline = context.ApiDescription.ActionDescriptor.FilterDescriptors;
      var isAuthorized = filterPipeline.Select(filterInfo => filterInfo.Filter).Any(filter => filter is AuthorizeFilter);
      var allowAnonymous = filterPipeline.Select(filterInfo => filterInfo.Filter).Any(filter => filter is IAllowAnonymousFilter);

      if (isAuthorized && !allowAnonymous)
      {
          if (operation.Parameters == null)
             operation.Parameters = new List<IParameter>();

          operation.Parameters.Add(new NonBodyParameter
          {                    
             Name = "Authorization",
             In = "header",
             Description = "access token",
             Required = true,
             Type = "string"
         });
      }
   }
}

Then you will see an extra Authorization TextBox in your swagger where you can add your token in the format ‘Bearer {jwttoken}’ and you should be authorized in your swagger requests.