allow cancellation of call using dio cancellation

[rgplvr]

allow cancellation of call using dio cancellation

[knaeckeKami]

Hello, thanks for the PR. It seems there is an issue with the CI, looks like a breaking change in one of the dependencies of multipack. I'll try to fix it.

Support for cancellation in Dio is good, but is passing a signal cancel token for all requests of the link the right approach?

You can only cancel the token once, right?

I think a better solution would be to pass the cancel token via the context. Then the client code could either create a new cancel token for each request or re-use the same token for multiple requests if preferred.

See e.g. https://github.com/gql-dart/gql/blob/master/links/gql_dio_link/lib/src/dio_link.dart#L312

class DioLinkCancelTokenContextEntry extends ContextEntry {

     final CancelToken token;

     ...
}

in DioLink:

...
final cancelToken = request.context.entry<DioLinkCancelTokenContextEntry>();

...

[rgplvr]

Makes sense. I have made the changes to push the cancellation token to the context entry.

[knaeckeKami]

please update your branch from master to fix the ci issues

[rgplvr]

done

[rgplvr]

made the changes the source is properly formatted as per the diff

[knaeckeKami]

Thanks, LGTM