package main

import (
    "mime"
    "fmt"
)

func main() {
    sdata := "0"
    mt, params, err := mime.ParseMediaType(sdata)
    if err != nil {
        return
    }
    sdata1 := mime.FormatMediaType(mt, params)
    _, _, err = mime.ParseMediaType(sdata1)
    if err != nil {
        fmt.Printf("%q(%q, %+v) -> %q\n", sdata, mt, params, sdata1)
        panic(err)
    }
}