globaltracer.go
func StartSpan(operationName string, opts ...StartSpanOption) Span {
	return globalTracer.tracer.StartSpan(operationName, opts...)
}
func StartSpan(operationName string, opts ...StartSpanOption) Span {
	return globalTracer.tracer.StartSpan(operationName, opts...)
}
func StartSpan ( operationName string , opts ... StartSpanOption ) Span { return globalTracer . tracer . StartSpan ( operationName , opts ... ) }
// StartSpan defers to `Tracer.StartSpan`. See `GlobalTracer()`.
StartSpan defers to Tracer . StartSpan . See GlobalTracer () .