Allow OS to choose the best protocol to use

[lwalejko]

As per documentation (https://docs.microsoft.com/en-us/dotnet/api/system.security.authentication.sslprotocols?view=netframework-4.8), None should be used as default value, not Default, because Default allows only outdated and less secure protocols.

[eynzhang]

I agree with this as I encountered same issue when initializing the connection, and I found the same root cause while looking at the source code.

[lwalejko]

I forgot about this pull request to be honest ;)

@eynzhang have you tried if this change works for you as intended? I had some more problems with this and ended up using System.Security.Authentication.SslProtocols.Tls12 value directly.

[eynzhang]

I think that’s depends on the settings in server, in my cases ‘None’ is working for me.

That’s why I proposed a request on the readme document here:
#583

Maybe a better way is to pass this property by the constructor or a public method.