Generate simple random int using crypto/rand.

generateRandomInt.go

package main

import (
	"crypto/rand"
	"fmt"
	"math/big"
)

func main() {

	array := []int{1, 2, 3, 4}

	for {
		n, err := generateRandomInt(len(array))
		if err != nil {
			panic(err)
		}
		fmt.Println(n)
	}

}

// generateRandomInt returns an integer between 0 and max parameter.
// "Max" must be less than math.MaxInt32
func generateRandomInt(max int) (int, error) {
	result, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
	return int(result.Int64()), err
}