code: func (group *RouterGroup) StaticFile(relativePath, filepath string) IRoutes {
  	if strings.Contains(relativePath, ":") || strings.Contains(relativePath, "*") {
  		panic("URL parameters can not be used when serving a static file")
  	}
  	handler := func(c *Context) {
  		c.File(filepath)
  	}
  	group.GET(relativePath, handler)
  	group.HEAD(relativePath, handler)
  	return group.returnObj()
  }
docs: // StaticFile registers a single route in order to serve a single file of the local filesystem.
  // router.StaticFile("favicon.ico", "./resources/favicon.ico")