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event-stream" after migrating to .NetCore 2.0

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I have an existing SPA based on Asp .Net Core (I was using Yo generator-aspnetcore-spa to generate a template). It worked perfectly fine, but after migration to .NetCore 2.0 it started to throw the error:

EventSource's response has a MIME type ("text/html") that is not "text/event-stream". Aborting the connection.

As I understood this problem affects only auto-refresh after updating any file (hot module replacement as far as I know). All other stuff is working fine.

So, the question is how to fix the error above?

I found the solution, mainly the problem is in .NetCore routing system, it is taking over and trying to handle the request, returning text/html, so it's sending the actual webpack_hmr hot file. To fix it you need to edit Configure method in the Startup.cs file.

Before:

// some code
app.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions {
            HotModuleReplacement = true                    
//some code
After:
// some code
app.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions {
            HotModuleReplacement = true,
            HotModuleReplacementEndpoint = "/dist/__webpack_hmr"                   
// some code
The solution is taken from this thread on GitHub
Check whether your Hosting environment is set to Production or to Development (Webpack HMR is disabled for Production)
Change the Hosting environment to Development.

Add export ASPNETCORE_ENVIRONMENT=development to your ~/.bash_profile or ~/.zshrc file.
Follow the link for more exhaustive explanation.
Thus your output should be:
This link explains how to change the env in more depth.
                The problem existed for the development environment. Everything was working before migration to .net core 2
– Serg.ID
                Oct 21, 2017 at 1:43
                I tried your your answer and it didn't work. Then the link at my 2nd point fixed my error. The problem was my hosting env.
– Eddy Ekofo
                Oct 21, 2017 at 9:32
                From this point of view you are absolutely right, HMR works only in Dev env. However, this quetion was about “EventSource's response has a MIME type ("text/html")” error
– Serg.ID
                Oct 21, 2017 at 20:56
                You're right! this the same error I also got but my problem was different I guess, and I was able to resolve it by changing the Hosting env.
– Eddy Ekofo
                Oct 21, 2017 at 21:41
                @Serg.ID Still Unable to figure out this. After deployed, our env is not Dev then how to handle this issue? there it won't use any HMR.
– k11k2
                Dec 12, 2017 at 16:28
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