code: func Serve(urlPrefix string, fs ServeFileSystem) gin.HandlerFunc {
  	fileserver := http.FileServer(fs)
  	if urlPrefix != "" {
  		fileserver = http.StripPrefix(urlPrefix, fileserver)
  	}
  	return func(c *gin.Context) {
  		if fs.Exists(urlPrefix, c.Request.URL.Path) {
  			fileserver.ServeHTTP(c.Writer, c.Request)
  			c.Abort()
  		}
  	}
  }
docs: // Static returns a middleware handler that serves static files in the given directory.