minor typo in routergroup.go (#1360)

routergroup.go

@@ -139,7 +139,7 @@ func (group *RouterGroup) Any(relativePath string, handlers ...HandlerFunc) IRou
 	return group.returnObj()
 }
 
-// StaticFile registers a single route in order to server a single file of the local filesystem.
+// StaticFile registers a single route in order to serve a single file of the local filesystem.
 // router.StaticFile("favicon.ico", "./resources/favicon.ico")
 func (group *RouterGroup) StaticFile(relativePath, filepath string) IRoutes {
 	if strings.Contains(relativePath, ":") || strings.Contains(relativePath, "*") {