Golang : Roll the dice example

Just a simple example on how to simulate dice rolling. Useful in situation where you need to use random single digit number to ensure different results very time.

UPDATE: The previous code used dice[rand.Intn(len(dice)-1)], which caused the dice to never reach the position 6 and also run rand.Seed(time.Now().UnixNano()) multiple times - which is an unnecessary overhead. The code below has been updated to correct the bug and rand.Seed() function only executes once throughout the duration of this program. Thanks to Patrik Lundin for pointing this out.

Here you go!

 package main

 import (
  "fmt"
  "math/rand"
  "sync"
  "time"
 )

 var onlyOnce sync.Once

 // prepare the dice 
 var dice = []int{1, 2, 3, 4, 5, 6}

 func rollDice() int {

  onlyOnce.Do(func() {
 rand.Seed(time.Now().UnixNano()) // only run once
  })

  return dice[rand.Intn(len(dice))]
 }

 func main() {
  dice1 := rollDice()
  dice2 := rollDice()
  dice3 := rollDice()

  fmt.Println("Dice 1: ", dice1)
  fmt.Println("Dice 2: ", dice2)
  fmt.Println("Dice 3: ", dice3)
 }

Sample output:

Dice 1: 6

Dice 2: 2

Dice 3: 2

Dice 1: 5

Dice 2: 1

Dice 3: 3

Happy coding!

Reference:

https://www.socketloop.com/tutorials/golang-how-to-run-your-code-only-once-with-sync-once-object