Proxy mode: Unhandled exception when target is not working

[LevYas]

WireMock returns stack trace instead of a meaningful message, it is very misleading.
Repro: https://github.com/LevYas/WireMockNetRepro

It would be very nice to return a message, saying that the target is not available.

[StefH]

Preview version WireMock.Net.1.2.10-ci-13352 on MyGet should fix this 500 error, please test.

[LevYas]

Tested. For me, it doesn't return "No such host is known.", but "No connection could be made because the target machine actively refused it.":

< HTTP/1.1 100 Continue
< HTTP/1.1 500 Internal Server Error
...
* HTTP error before end of send, stop sending
<
{"Status":"No connection could be made because the target machine actively refused it."}* Closing connection 0

Anyway, it's much better than a stack trace :D
But I think the test in your PR might not be stable.

[StefH]

I run the tests for netcore 3.1 and I noticed a difference there, so I just check on known.

[LevYas]

I also used netcore 3.1, but on Windows, maybe that's the reason

[StefH]

OK, the difference is that I try to connect to a non-existing hostname.
And you try to connect to localhost (which exists) but nothing listens at port 5000.

[LevYas]

Ah, sure, you are right, thanks.

[StefH]

I'll merge to master. New NuGet will be released soon.