This exercise does not have any specific code examples or even recommendations. Instead, it's an invitation to go and explore the large amount of community-contributed instrumentation libraries listed in the OpenTracing Registry [5]. Check whether a framework you are using in your application is already supported there and give it a try. If it's not supported, maybe use the skills you acquired by reading this chapter to contribute a new module. Alternatively, if you know the developers of the framework, ask them to add OpenTracing instrumentation and enable tracing in their framework.
Another option to explore for "extra credit" is trying to use the same Hello application with a different implementation of OpenTracing. You can find OpenTracing-compatible libraries for Zipkin, and for other tracing systems [5], both free and commercial. The only places that need changing in the exercises are the InitTracer functions.