code: func (t *Tracer) Send(ctx context.Context, r *request.Request, opts ...Option) error {
  	span, ctx := opentracing.StartSpanFromContext(ctx, "client.request")
  	defer span.Finish()
  
  	r.HTTPRequest = r.HTTPRequest.WithContext(ctx)
  	err := r.Send()
  
  	opts = append(t.Opts, opts...)
  	for _, fn := range opts {
  		fn(span, r, err)
  	}
  
  	return err
  }
docs: // Send wraps the aws request with an opentracing span.
  //
  // req, output := dynamoClient.PutItemRequest(input)
  // err := t.Send(ctx, req)