Asp.Net Core 2.0: an easy way to complete long-term tasks and report on progress?

Question

I have a page where the user can select several files and upload them.

Once the files are buffered on the server, they are deserialized and the object graphs are stored using Entity Framework Core 2 and SQL Server.

All this happens in the action of the controller.

The problem is that when the file is a little larger, this set of tasks can take about 5 minutes, and because of this I get error 502 (probably timeout).

To solve this problem, I had the idea to report on progress. Thus, this will prevent a timeout. I researched, and some people suggested using SignalR. But I found out that SignalR is not yet available for Asp.Net Core.

So, how can I solve this problem basically? I would like to report on the progress of my controller. But if this is complicated material, then how can I prevent a timeout?

I am using Angular 4.3.5, by the way.