Add custom instrumentation and context propagation in sample apps

[srikanthccv]

Having a simple custom span that demonstrates how to make the context propagation work in sample apps will help users write their own. This is simple in languages such as Java, Python where the implicit context takes cares but languages such as go require the correct context.Context to be passed.

[rvyash]

Hey @srikanthccv I wanted to know if anyone is working on this issue.

[srikanthccv]

would you like to work on this?

[rvyash]

Yes, I'm interested in working on this issue.

Before I start, let me clarify my understanding of the issue. We need a sample Go application that must be instrumented and should include a custom span demonstrating Context Propagation. If I've misunderstood anything, please let me know.

[srikanthccv]

Yes, your understanding is correct.