fix golint warnings

mux.go

@@ -363,9 +363,9 @@ func (r *Router) Walk(walkFn WalkFunc) error {
 	return r.walk(walkFn, []*Route{})
 }
 
-// SkipRouter is used as a return value from WalkFuncs to indicate that the
+// ErrSkipRouter is used as a return value from WalkFuncs to indicate that the
 // router that walk is about to descend down to should be skipped.
-var SkipRouter = errors.New("skip this router")
+var ErrSkipRouter = errors.New("skip this router")
 
 // WalkFunc is the type of the function called for each route visited by Walk.
 // At every invocation, it is given the current route, and the current router,
@@ -375,7 +375,7 @@ type WalkFunc func(route *Route, router *Router, ancestors []*Route) error
 func (r *Router) walk(walkFn WalkFunc, ancestors []*Route) error {
 	for _, t := range r.routes {
 		err := walkFn(t, r, ancestors)
-		if err == SkipRouter {
+		if err == ErrSkipRouter {
 			continue
 		}
 		if err != nil {

mux_test.go

@@ -1600,7 +1600,7 @@ func TestWalkSingleDepth(t *testing.T) {
 	err := r0.Walk(func(route *Route, router *Router, ancestors []*Route) error {
 		matcher := route.matchers[0].(*routeRegexp)
 		if matcher.template == "/d" {
-			return SkipRouter
+			return ErrSkipRouter
 		}
 		if len(ancestors) != depths[i] {
 			t.Errorf(`Expected depth of %d at i = %d; got "%d"`, depths[i], i, len(ancestors))

regexp_test.go

@@ -54,7 +54,7 @@ func Benchmark_findQueryKey(b *testing.B) {
 			b.ReportAllocs()
 			b.ResetTimer()
 			for i := 0; i < b.N; i++ {
-				for key, _ := range all {
+				for key := range all {
 					_, _ = findFirstQueryKey(query, key)
 				}
 			}
@@ -79,7 +79,7 @@ func Benchmark_findQueryKeyGoLib(b *testing.B) {
 			b.ReportAllocs()
 			b.ResetTimer()
 			for i := 0; i < b.N; i++ {
-				for key, _ := range all {
+				for key := range all {
 					v := u.Query()[key]
 					if len(v) > 0 {
 						_ = v[0]