code: func (c *ctx) spanIsSampled(sp opentracing.Span) bool {
  	jaegerSpan, ok := sp.(*jaeger.Span)
  	if !ok {
  		return false
  	}
  
  	jaegerCtx := jaegerSpan.Context()
  	spanCtx, ok := jaegerCtx.(*jaeger.SpanContext)
  	if !ok {
  		return false
  	}
  
  	if !spanCtx.IsSampled() {
  		return false
  	}
  
  	return true
  }
docs: // Until OpenTracing supports the `IsSampled()` method, we need to cast to a Jaeger span.
  // See https://github.com/opentracing/specification/issues/92 for more information.