Use scheme from parent router when building URLs.

mux.go

@@ -176,6 +176,13 @@ func (r *Router) UseEncodedPath() *Router {
 // parentRoute
 // ----------------------------------------------------------------------------
 
+func (r *Router) getBuildScheme() string {
+	if r.parent != nil {
+		return r.parent.getBuildScheme()
+	}
+	return ""
+}
+
 // getNamedRoutes returns the map where named routes are registered.
 func (r *Router) getNamedRoutes() map[string]*Route {
 	if r.namedRoutes == nil {

mux_test.go

@@ -1215,6 +1215,17 @@ func TestSubRouter(t *testing.T) {
 			pathTemplate: `/{category}`,
 			shouldMatch:  true,
 		},
+		{
+			title:        "Build with scheme on parent router",
+			route:        new(Route).Schemes("ftp").Host("google.com").Subrouter().Path("/"),
+			request:      newRequest("GET", "ftp://google.com/"),
+			scheme:       "ftp",
+			host:         "google.com",
+			path:         "/",
+			pathTemplate: `/`,
+			hostTemplate: `google.com`,
+			shouldMatch:  true,
+		},
 	}
 
 	for _, test := range tests {

route.go

@@ -396,7 +396,7 @@ func (r *Route) Schemes(schemes ...string) *Route {
 	for k, v := range schemes {
 		schemes[k] = strings.ToLower(v)
 	}
-	if r.buildScheme == "" && len(schemes) > 0 {
+	if r.getBuildScheme() == "" && len(schemes) > 0 {
 		r.buildScheme = schemes[0]
 	}
 	return r.addMatcher(schemeMatcher(schemes))
@@ -488,8 +488,8 @@ func (r *Route) URL(pairs ...string) (*url.URL, error) {
 			return nil, err
 		}
 		scheme = "http"
-		if r.buildScheme != "" {
+		if s := r.getBuildScheme(); s != "" {
-			scheme = r.buildScheme
+			scheme = s
 		}
 	}
 	if r.regexp.path != nil {
@@ -534,8 +534,8 @@ func (r *Route) URLHost(pairs ...string) (*url.URL, error) {
 		Scheme: "http",
 		Host:   host,
 	}
-	if r.buildScheme != "" {
+	if s := r.getBuildScheme(); s != "" {
-		u.Scheme = r.buildScheme
+		u.Scheme = s
 	}
 	return u, nil
 }
@@ -649,11 +649,22 @@ func (r *Route) buildVars(m map[string]string) map[string]string {
 
 // parentRoute allows routes to know about parent host and path definitions.
 type parentRoute interface {
+	getBuildScheme() string
 	getNamedRoutes() map[string]*Route
 	getRegexpGroup() *routeRegexpGroup
 	buildVars(map[string]string) map[string]string
 }
 
+func (r *Route) getBuildScheme() string {
+	if r.buildScheme != "" {
+		return r.buildScheme
+	}
+	if r.parent != nil {
+		return r.parent.getBuildScheme()
+	}
+	return ""
+}
+
 // getNamedRoutes returns the map where named routes are registered.
 func (r *Route) getNamedRoutes() map[string]*Route {
 	if r.parent == nil {