Improve example, add go module

[VojtechVitek]

No description provided.

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │               pr.txt               │
               │   sec/op    │   sec/op     vs base               │
LocalCounter-4   19.78m ± 1%   19.53m ± 1%  -1.26% (p=0.007 n=10)

               │  master.txt  │               pr.txt                │
               │     B/op     │     B/op      vs base               │
LocalCounter-4   2.828Mi ± 0%   2.834Mi ± 0%  +0.21% (p=0.007 n=10)

               │ master.txt  │               pr.txt               │
               │  allocs/op  │  allocs/op   vs base               │
LocalCounter-4   121.4k ± 0%   121.5k ± 0%  +0.05% (p=0.007 n=10)

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │            pr.txt             │
               │   sec/op    │   sec/op     vs base          │
LocalCounter-4   19.84m ± 0%   19.86m ± 1%  ~ (p=0.436 n=10)

               │  master.txt  │             pr.txt             │
               │     B/op     │     B/op      vs base          │
LocalCounter-4   2.836Mi ± 0%   2.833Mi ± 0%  ~ (p=0.123 n=10)

               │ master.txt  │            pr.txt             │
               │  allocs/op  │  allocs/op   vs base          │
LocalCounter-4   121.5k ± 0%   121.5k ± 0%  ~ (p=0.123 n=10)