code: func NewClientWrapper(ot opentracing.Tracer) client.Wrapper {
  	return func(c client.Client) client.Client {
  		if ot == nil {
  			ot = opentracing.GlobalTracer()
  		}
  		return &otWrapper{ot, c}
  	}
  }
docs: // NewClientWrapper accepts an open tracing Trace and returns a Client Wrapper