browser return application/octet-stream (0 byte) when url TrailingSlash

[tablecell]

package main

import (
    "bytes"
    "github.com/aofei/air"
 )

var a = air.Default

func identicon(req *air.Request, res *air.Response) error {
    return res.Write(bytes.NewReader(req.ParamValue("Name").Bytes()))
}
func main() {
    a.DebugMode = true

    a.GET("/identicons/:Name", identicon)
    a.Serve() //8080 
}

visit http://localhost:8080/identicons/