ASP.Net Core middleware v1.2 incompatible with zipkin4net v1.1

[adamrodger]

The zipkin4net.middleware.aspnetcore package declares a dependency of >= 1.1.0 on zipkin4net, but it is not actually compatible with that version:

System.MissingMethodException: Method not found: 'Void zipkin4net.Transport.Http.TracingHandler..ctor(System.String, System.Net.Http.HttpMessageHandler)'.

This is because an extra optional argument has been added to the constructor of TracingHandler in v1.2.0 which is not present in v1.1.0.

If you force your app to use v1.2.0 of both libraries then it works fine, but if you just install the middleware and take the transitive dependency on v1.1.0 then you'll get the above runtime exception.

[fedj]

It's weird as we don't really specify explicit versioning for this. aspnetcore 1.2.0 should target zipkin4net 1.2.0.

I think the problem comes from https://github.com/openzipkin/zipkin4net/blob/master/Src/zipkin4net.middleware.aspnetcore/Src/zipkin4net.middleware.aspnetcore.csproj#L9.

Would you be able to come up with a PR ?