jQuery到Golang的POST破坏了字段名

I have a JQuery script which includes the line

console.log("Killing "+selected)
$.post("http://127.0.0.1:8080/delete_birloki",{ birloki: selected})

and it logs...

Killing france

The Golang handler starts with

func deleteBirloki(rw http.ResponseWriter, req *http.Request) {
    dat,err := httputil.DumpRequest(req,true)
    if err != nil {
        fmt.Fprintf(rw,"BAD")
        return
    }
    fmt.Println(string(dat))

and the print out is

POST /delete_birloki HTTP/1.1
Host: 127.0.0.1:8080
Accept: */*
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Cookie: weve_been_here_before=true; _ga=GA1.1.606577919.1412775218
Origin: http://127.0.0.1:8080
Referer: http://127.0.0.1:8080/config/?birloki=&north=&east=
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.111 Safari/537.36
X-Requested-With: XMLHttpRequest

birloki%5B%5D=france

Can anybody explain WHY the variable name has been changed? in a similar case I could request for "birloki[]" with

birloki := req.PostFormValue("birloki[]")

but even that does not seem to work in this case

OK - shoot me. I am an idiot.

Due to the lovely untyped nature of Javascript, the variable I was posting was sometimes a string and sometimes an array.

When it appeared with [] it was, of course, an array :-(