This example demonstrates how to use go-httpbin's Observer mechanism to
add custom instrumentation to a go-httpbin instance.
An observer is a function that will be called with an httpbin.Result
struct after every request, which provides a hook for custom logging, metrics,
or other instrumentation.
Note: This does require building your own small wrapper around go-httpbin, as you can see in main.go here. That's because go-httpbin has no dependencies outside of the Go stdlib, to make sure that it is as safe/lightweight as possible to include as a dependency in other applications' test suites where useful.