Fix extraction for zipkin tracing

pkg/tracing/carrier.go

@@ -1,25 +0,0 @@
-package tracing
-
-import "net/http"
-
-// HTTPHeadersCarrier custom implementation to fix duplicated headers
-// It has been fixed in https://github.com/opentracing/opentracing-go/pull/191
-type HTTPHeadersCarrier http.Header
-
-// Set conforms to the TextMapWriter interface.
-func (c HTTPHeadersCarrier) Set(key, val string) {
-	h := http.Header(c)
-	h.Set(key, val)
-}
-
-// ForeachKey conforms to the TextMapReader interface.
-func (c HTTPHeadersCarrier) ForeachKey(handler func(key, val string) error) error {
-	for k, vals := range c {
-		for _, v := range vals {
-			if err := handler(k, v); err != nil {
-				return err
-			}
-		}
-	}
-	return nil
-}

pkg/tracing/tracing.go

@@ -134,7 +134,7 @@ func InjectRequestHeaders(r *http.Request) {
 		err := opentracing.GlobalTracer().Inject(
 			span.Context(),
 			opentracing.HTTPHeaders,
-			HTTPHeadersCarrier(r.Header))
+			opentracing.HTTPHeadersCarrier(r.Header))
 		if err != nil {
 			log.FromContext(r.Context()).Error(err)
 		}