[go-nuts] panic: cant Decode gob file

I want to save/load data on gob file, so I Created "example.gob" and try to
save custom struct.. and It fail


package main

import (
     "encoding/gob"
     "os"
)

type Person struct {
     Title string
}
type Persons []Person

func (p *Persons) add(pp Person) {
     *p = append(*p, Person{pp.Title})
}

func IdxSave( page Persons) {
     f, err := os.Open("./example.gob")
     if err != nil {
         panic("cant open file")
     }
     defer f.Close()

     enc := gob.NewEncoder(f)
     if err := enc.Encode(page); err != nil {
         panic("cant encode")
     }
}

func main() {
      IdxSave(Persons{Person{"Hans"}})
}


when I see the log. it say " bad file descriptor" and some go routine which
I can't understand
how can I solved?