router: move context params stuff to router.go

Author: julienschmidt

params.go

@@ -77,6 +77,7 @@
 package httprouter
 
 import (
+	"context"
 	"net/http"
 )
 
@@ -107,6 +108,18 @@ func (ps Params) ByName(name string) string {
 	return ""
 }
 
+type paramsKey struct{}
+
+// ParamsKey is the request context key under which URL params are stored.
+var ParamsKey = paramsKey{}
+
+// ParamsFromContext pulls the URL parameters from a request context,
+// or returns nil if none are present.
+func ParamsFromContext(ctx context.Context) Params {
+	p, _ := ctx.Value(ParamsKey).(Params)
+	return p
+}
+
 // Router is a http.Handler which can be used to dispatch requests to different
 // handler functions via configurable routes
 type Router struct {
@@ -236,6 +249,20 @@ func (r *Router) Handle(method, path string, handle Handle) {
 	root.addRoute(path, handle)
 }
 
+// Handler is an adapter which allows the usage of an http.Handler as a
+// request handle.
+// The Params are available in the request context under ParamsKey.
+func (r *Router) Handler(method, path string, handler http.Handler) {
+	r.Handle(method, path,
+		func(w http.ResponseWriter, req *http.Request, p Params) {
+			ctx := req.Context()
+			ctx = context.WithValue(ctx, ParamsKey, p)
+			req = req.WithContext(ctx)
+			handler.ServeHTTP(w, req)
+		},
+	)
+}
+
 // HandlerFunc is an adapter which allows the usage of an http.HandlerFunc as a
 // request handle.
 func (r *Router) HandlerFunc(method, path string, handler http.HandlerFunc) {