Overview

‘mat/rand’ package of golang contains a Intn function that can be used to generate a random number between [0,n). Bracket at the end means that n is exclusive.

To know more about what pseudo-random number means, checkout this post – https://golangbyexample.com/generate-random-number-golang

Below is the signature of this method. It takes input a number n and will return a number x in range 0<=x<n.

func Intn(n int) int

Above function can also be used to generate a random number in range a to b too. See below program. It is used to generate a number between range a to b. We are also providing a seed value to the rand so that it generates different output everytime.

Code

package main

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

func main() {
    rand.Seed(time.Now().Unix())

    //Generate a random number x where x is in range 5<=x<=20
    rangeLower := 5
    rangeUpper := 20
    randomNum := rangeLower + rand.Intn(rangeUpper-rangeLower+1)
    fmt.Println(randomNum)

    //Generate a random number x where x is in range 100<=x<=200
    rangeLower = 100
    rangeUpper = 200
    randomNum = rangeLower + rand.Intn(rangeUpper-rangeLower+1)
    fmt.Println(randomNum)
}

Output:

Number between 5<=x<=20
Number between 100<=x<=200