* Routing of requests is done in the context of network IO, perhaps disk IO and likely database accesses. The 500 nanoseconds you shave off your request time are likely not worth the trouble you went through, given that a HTTP request sending the bytes of the header will usually amount to a few hundred microseconds, milliseconds with some body. I'd suggest you attack the problem of performance by profiling bottlenecks, to identify parts of your code that have the greatest impact on the request time.
* The benchmark you wrote is not testing your claim (of fast routing/multiplexing), since the benchmark works against a router with no registered routes. When benchmarketing, I'd suggest creating a realistic scenario, a scenario your users are likely to end up with. In your case, this would likely mean a dozen resources, each with about 5 routes, using all verbs.
This blog post is very useful to begin with optimization work in Go: http://blog.golang.org/profiling-go-programs