supporting unlimited cache size for router matching

Author: jkyberneees

docs/README.md

@@ -97,7 +97,7 @@ server.listen(3000)
     res.end()
   }
   ```
-- **cacheSize**: Router matching LRU cache size. A given value <= 0 will disable the cache. Default value: `1000`
+- **cacheSize**: The size of the LRU cache for router matching. If the value is `0`, the cache will be disabled. If the value is `<0`, the cache will have an unlimited size. If the value is `>0`, an LRU Cache will be used. Default value: `-1`, for extreme performance.
 - **errorHandler**: Global error handler function. Default value: 
 
   ```js 

lib/router/sequential.js

@@ -1,7 +1,7 @@
 const { Trouter } = require('trouter')
 const next = require('./../next')
-const { LRUCache: LRU } = require('lru-cache')
 const { parse } = require('regexparam')
+const { LRUCache: Cache } = require('lru-cache')
 const queryparams = require('../utils/queryparams')
 
 module.exports = (config = {}) => {
@@ -18,15 +18,19 @@ module.exports = (config = {}) => {
     }
   }
   if (config.cacheSize === undefined) {
-    config.cacheSize = 1000
+    config.cacheSize = -1
   }
   if (config.id === undefined) {
     config.id = (Date.now().toString(36) + Math.random().toString(36).substr(2, 5)).toUpperCase()
   }
 
   const routers = {}
-  const isCacheEnabled = config.cacheSize > 0
-  const cache = isCacheEnabled ? new LRU({ max: config.cacheSize }) : null
+  let cache = null
+  if (config.cacheSize > 0) {
+    cache = new Cache({ max: config.cacheSize })
+  } else if (config.cacheSize < 0) {
+    cache = new Map()
+  }
   const router = new Trouter()
   router.id = config.id
 
@@ -59,7 +63,7 @@ module.exports = (config = {}) => {
     queryparams(req, req.url)
 
     let match
-    if (isCacheEnabled) {
+    if (cache) {
       const reqCacheKey = req.method + req.path
       match = cache.get(reqCacheKey)
       if (!match) {