请求路由和分发的 Go 框架 gorilla/mux
`gorilla/mux` 实现了一个请求路由和分发的 Go 框架。
mux 名字的意思是 "HTTP request multiplexer". 和标准包 `http.ServeMux`类似， `mux.Router`根据已注册路由列表匹配传入请求，并调用与URL或其他条件匹配的路由的处理程序。
主要特性：
* It implements the `http.Handler` interface so it is compatible with the standard `http.ServeMux`.
* Requests can be matched based on URL host, path, path prefix, schemes, header and query values, HTTP methods or using custom matchers.
* URL hosts, paths and query values can have variables with an optional regular expression.
* Registered URLs can be built, or "reversed", which helps maintaining references to resources.
* Routes can be used as subrouters: nested routes are only tested if the parent route matches. This is useful to define groups of routes that share common conditions like a host, a path prefix or other repeated attributes. As a bonus, this optimizes request matching.
## 安装
<pre>go get -u github.com/gorilla/mux</pre>
## 代码示例
<pre>func main() {
r := mux.NewRouter()
r.HandleFunc("/", HomeHandler)
r.HandleFunc("/products", ProductsHandler)
r.HandleFunc("/articles", ArticlesHandler)
http.Handle("/", r)
}</pre>
这里我们注册了三个 URL 匹配路由进行处理。路径也可以是变量：
<pre>r := mux.NewRouter()
r.HandleFunc("/products/{key}", ProductHandler)
r.HandleFunc("/articles/{category}/", ArticlesCategoryHandler)
r.HandleFunc("/articles/{category}/{id:[0-9]+}", ArticleHandler)</pre>
这些名称用于创建路由变量的映射，可以通过调用mux.Vars 获取：
<pre>func ArticlesCategoryHandler(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
w.WriteHeader(http.StatusOK)
fmt.Fprintf(w, "Category: %v\n", vars["category"])
}
</pre>
