Added support for Haystack tracing

vendor/github.com/ExpediaDotCom/haystack-client-go/tracer_options.go

@@ -0,0 +1,59 @@
+/*
+ *  Copyright 2018 Expedia Group.
+ *
+ *     Licensed under the Apache License, Version 2.0 (the "License");
+ *     you may not use this file except in compliance with the License.
+ *     You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *     Unless required by applicable law or agreed to in writing, software
+ *     distributed under the License is distributed on an "AS IS" BASIS,
+ *     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *     See the License for the specific language governing permissions and
+ *     limitations under the License.
+ *
+ */
+
+package haystack
+
+import (
+	"github.com/opentracing/opentracing-go"
+)
+
+// TracerOption is a function that sets some option on the tracer
+type TracerOption func(tracer *Tracer)
+
+/*TracerOptions a list of tracer options*/
+type TracerOptions struct{}
+
+/*TracerOptionsFactory factory to create multiple tracer options*/
+var TracerOptionsFactory TracerOptions
+
+/*Propagator registers a new Propagator*/
+func (t TracerOptions) Propagator(format interface{}, propagator Propagator) TracerOption {
+	return func(tracer *Tracer) {
+		tracer.propagators[format] = propagator
+	}
+}
+
+/*Tag adds a common tag in every span*/
+func (t TracerOptions) Tag(key string, value interface{}) TracerOption {
+	return func(tracer *Tracer) {
+		tracer.commonTags = append(tracer.commonTags, opentracing.Tag{Key: key, Value: value})
+	}
+}
+
+/*Logger set the logger type*/
+func (t TracerOptions) Logger(logger Logger) TracerOption {
+	return func(tracer *Tracer) {
+		tracer.logger = logger
+	}
+}
+
+/*UseDualSpanMode sets the tracer in dual span mode*/
+func (t TracerOptions) UseDualSpanMode() TracerOption {
+	return func(tracer *Tracer) {
+		tracer.useDualSpanMode = true
+	}
+}