* WIP
* Finish http middleware implementation
This is currently done as httptrace.NewHandler(). This should maybe
be moved to a different package or renamed, but atm this name
seemed the least objectionable to me.
There are a few TODOs sprinkled in the code for questions I didn't
know the answers to.
There is an example provided, which when copied to a main func
locally work against the jaeger all in one.
Real tests need to be added.
* Address feedback
* Tie in propagation, update attributes, more options, revise example, etc.
Dropped the httpConfig type because it seemed redundant an unecessary
abstraction.
* WithRouteTag
* address out of band feedback
* move to othttp package
* Add a very basic test.
I ended up needing to export the Traceparentheader const so that
it was accessible to this test.
* Add file header
* add propagation api.
* add http propagator interface and w3c propagator implementation.
* remove Extract api from trace.
* remove Extract interface for tracer.
* fix copyright.
* fix variable names and comments.
* move inject/extract out of trace.
* replace INVALID_SPAN_CONTEXT with EmptySpanContext function.
* fix tag.Map.
* make carrier as interface instead of http.Request.
* rename structs and update doc comments..
* add doc.go
* update doc.
* add noop propagator.
* add new propagation api with Supplier interface.
- added Default Tracer which simply propagates SpanContext.
- added CopyOfRemote option to simply create remote span.
* remove old propagator.
* rename propagator to TextFormatPropagator.
* rename default tracer/span as pass_through tracer/span.
* add test for pass through tracer.
* add missing interface to pass through tracer.
* return SpanContext instead of contex.Context from Extract interface.
- also remove PassThroughTracer
* fix review comments.
* add more test cases for traceContext extraction.
* remove tidy temporarily from circle-ci target to avoid build failure.
* allow header ending in dash '-'.
* add inject test for non-zero value other than 01 for traceoption
* add AddLink and Link interface to MockSpan
* fix running go mod tidy on every build.
