How to create a 10MB file filled with "000000..." data in golang?

I am intended to use fdatasync in a system like log or diskqueue. The first thing is to create a 10MB file with "000000..." in file system like ext4. But I don't know how to do it properly.

jnml@fsc-r630:~/src/tmp/SO/16797380$ ls -l
celkem 4
-rw-rw-r-- 1 jnml jnml 186 kvě 29 07:54 main.go
jnml@fsc-r630:~/src/tmp/SO/16797380$ cat main.go 
package main

import (
        "log"
        "os"
)

func main() {
        f, err := os.Create("foo.bar")
        if err != nil {
                log.Fatal(err)
        }

        if err := f.Truncate(1e7); err != nil {
                log.Fatal(err)
        }
}
jnml@fsc-r630:~/src/tmp/SO/16797380$ go run main.go 
jnml@fsc-r630:~/src/tmp/SO/16797380$ ls -l
celkem 4
-rw-rw-r-- 1 jnml jnml 10000000 kvě 29 07:55 foo.bar
-rw-rw-r-- 1 jnml jnml      186 kvě 29 07:54 main.go
jnml@fsc-r630:~/src/tmp/SO/16797380$