使用 httputil.ReverseProxy 时 mux.Vars 为空

Question

我正在尝试同时使用 gorilla mux 和 httputil.ReverseProxy，但是在尝试获取 mux.Vars 时它是空的。根据https://golang.org/src/net/http/httputil/reverseproxy.go?s=2744:2819#L93似乎 http.Request 指针是原始请求的浅表副本，它应该仍然有效.有任何想法吗？https://play.golang.org/p/JpjNvEMIFBpackage mainimport (    "github.com/gorilla/mux"    "log"    "net/http"    "net/http/httputil"    "net/url")type route struct {    match string    base  string}var routes = []route{    // proxy http://localhost:3000/api/foo/bar => https://api.bar.com/5/foo/bar    route{match: "/api/{path}", base: "https://api.bar.com/5"},    route{match: "/sales/{path}", base: "https://sales.bar.com/3"},}func NewProxy(r *route) http.Handler {    director := func(req *http.Request) {        out, _ := url.Parse(r.base)        req.URL.Scheme = out.Scheme        req.URL.Host = out.Host        req.URL.Path = out.Path + "/" + mux.Vars(req)["path"] // mux Vars are empty here    }    return &httputil.ReverseProxy{Director: director}}func main() {    for _, route := range routes {        http.Handle(route.match, NewProxy(&route))    }    log.Println("Listening on port 8080")    http.ListenAndServe(":8080", nil)}