Remove/cleanup request context helpers (#525)

* Remove context helpers in context.go
* Update request context funcs to take concrete types
* Move TestNativeContextMiddleware to mux_test.go
* Clarify KeepContext Go 1.7+ comment

Mux doesn't build on Go < 1.7 so the comment doesn't really need to
clarify anymore.

mux.go

@@ -5,6 +5,7 @@
 package mux
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net/http"
@@ -58,8 +59,7 @@ type Router struct {
 
 	// If true, do not clear the request context after handling the request.
 	//
-	// Deprecated: No effect when go1.7+ is used, since the context is stored
-	// on the request itself.
+	// Deprecated: No effect, since the context is stored on the request itself.
 	KeepContext bool
 
 	// Slice of middlewares to be called after a match is found
@@ -195,8 +195,8 @@ func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	var handler http.Handler
 	if r.Match(req, &match) {
 		handler = match.Handler
-		req = setVars(req, match.Vars)
-		req = setCurrentRoute(req, match.Route)
+		req = requestWithVars(req, match.Vars)
+		req = requestWithRoute(req, match.Route)
 	}
 
 	if handler == nil && match.MatchErr == ErrMethodMismatch {
@@ -426,7 +426,7 @@ const (
 
 // Vars returns the route variables for the current request, if any.
 func Vars(r *http.Request) map[string]string {
-	if rv := contextGet(r, varsKey); rv != nil {
+	if rv := r.Context().Value(varsKey); rv != nil {
 		return rv.(map[string]string)
 	}
 	return nil
@@ -438,18 +438,20 @@ func Vars(r *http.Request) map[string]string {
 // after the handler returns, unless the KeepContext option is set on the
 // Router.
 func CurrentRoute(r *http.Request) *Route {
-	if rv := contextGet(r, routeKey); rv != nil {
+	if rv := r.Context().Value(routeKey); rv != nil {
 		return rv.(*Route)
 	}
 	return nil
 }
 
-func setVars(r *http.Request, val interface{}) *http.Request {
-	return contextSet(r, varsKey, val)
+func requestWithVars(r *http.Request, vars map[string]string) *http.Request {
+	ctx := context.WithValue(r.Context(), varsKey, vars)
+	return r.WithContext(ctx)
 }
 
-func setCurrentRoute(r *http.Request, val interface{}) *http.Request {
-	return contextSet(r, routeKey, val)
+func requestWithRoute(r *http.Request, route *Route) *http.Request {
+	ctx := context.WithValue(r.Context(), routeKey, route)
+	return r.WithContext(ctx)
 }
 
 // ----------------------------------------------------------------------------

mux_test.go

@@ -7,6 +7,7 @@ package mux
 import (
 	"bufio"
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"io/ioutil"
@@ -16,6 +17,7 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+	"time"
 )
 
 func (r *Route) GoString() string {
@@ -2804,6 +2806,28 @@ func TestSubrouterNotFound(t *testing.T) {
 	}
 }
 
+func TestContextMiddleware(t *testing.T) {
+	withTimeout := func(h http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			ctx, cancel := context.WithTimeout(r.Context(), time.Minute)
+			defer cancel()
+			h.ServeHTTP(w, r.WithContext(ctx))
+		})
+	}
+
+	r := NewRouter()
+	r.Handle("/path/{foo}", withTimeout(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		vars := Vars(r)
+		if vars["foo"] != "bar" {
+			t.Fatal("Expected foo var to be set")
+		}
+	})))
+
+	rec := NewRecorder()
+	req := newRequest("GET", "/path/bar")
+	r.ServeHTTP(rec, req)
+}
+
 // mapToPairs converts a string map to a slice of string pairs
 func mapToPairs(m map[string]string) []string {
 	var i int

test_helpers.go

@@ -15,5 +15,5 @@ import "net/http"
 // can be set by making a route that captures the required variables,
 // starting a server and sending the request to that server.
 func SetURLVars(r *http.Request, val map[string]string) *http.Request {
-	return setVars(r, val)
+	return requestWithVars(r, val)
 }