Depending on your use case, another option is the math/rand package. Don’t do this if you’re generating numbers that need to be completely unpredictable. It can be helpful if you need to get results that are reproducible, though — just pass in the same seed you passed in the first time.
Here’s the classic “seed the generator with the current time and generate a number” program:
package main
import (
"fmt"
"math/rand"
"time"
)
func main() {
rand.Seed(time.Now().Unix())
fmt.Println(rand.Int())
}