Random numbers

Context

The math/rand package generates pseudo‑random numbers. For cryptographic randomness, use crypto/rand. Since Go 1.20, the global generator is seeded automatically.

Example

Generate integers, floats, and random permutations.

Code example

package main

import (
    "fmt"
    "math/rand"
)

func main() {
    fmt.Println(rand.Intn(100))       // 0-99
    fmt.Println(rand.Float64())       // 0.0-1.0
    fmt.Println(rand.Int())           // non‑negative

    // Permutation of [0..n)
    perm := rand.Perm(5)
    fmt.Println(perm)
}

Output (example)

42
0.123456789
1234567890123456789
[2 0 4 1 3]

Useful links

• math/rand package
• Go by Example: Random Numbers