Simplify code

Use a single append call instead of a ranged for loop.

mux.go

@@ -112,9 +112,7 @@ func copyRouteConf(r routeConf) routeConf {
 	}
 
 	c.matchers = make([]matcher, 0, len(r.matchers))
-	for _, m := range r.matchers {
-		c.matchers = append(c.matchers, m)
-	}
+	c.matchers = append(c.matchers, r.matchers...)
 
 	return c
 }