rghetia 83935b2558 Add propagator interface and W3C propagator (#85) ... * 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.		2019-09-23 11:51:32 -07:00
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client.go	Add propagator interface and W3C propagator (#85)	2019-09-23 11:51:32 -07:00