Difficulty with Go Rand package

Is there any Go function which returns true pseudo random number in every run? What I actually mean is, consider following code,

package main

import (
    "fmt"
    "rand"
)

func main() {
    fmt.Println(rand.Int31n(100))
}

Every time I execute this code, I get the same output. Is there a method that will return different, random results each time that it is called?