A third clever mechanism for passing contextual state to handlers from the web application framework or middleware is to hide the context within the request itself. Since the request contains dynamic map information such as request headers and form key/value pairs, it is fairly easy to embed new information into this existing structure.

A good example of this is the Vestigo URL Router: https://github.com/husobee/vestigo. This standalone URL router actually hides the request URL parameter names and values within form fields on the request structure itself. This allows the developer to access the contextual framework's supplied information, in this case, the URL parameter names and values, without the need to use a central map or use a modified function signature. What is striking about this design is that the developer using this web application framework will be able to get all of the URL parameters from the router within their application handlers without subscribing to a modified application handler function signature.