There are a lot of examples to use math/rand. However, should use crypto/rand if you want to generate an unpredictable random value. That's because crypto/rand uses getrandom(2) if available, /dev/urandom otherwise on Linux.
As a real world example, UUID v4 uses crypto/rand internally. UUID v4) is randomly generated. An implementation of UUID v4 in Go uses crypto/rand internally.
Here is an example to generate random values with crypto/rand.
Generate random integer
func generateInt(n int64) (int64, error) {
r, err := rand.Int(rand.Reader, big.NewInt(n))
if err != nil {
return 0, err
}
return r.Int64(), nil
}
Generate random string
func generateString(length int) (string, error) {
b := make([]byte, length)
_, err := rand.Read(b)
if err != nil {
return "", err
}
return base64.URLEncoding.EncodeToString(b), nil
}
Whole source code
package main
import (
"crypto/rand"
"encoding/base64"
"fmt"
"log"
"math/big"
)
func main() {
v, err := generateInt(1000)
if err != nil {
log.Fatal(err)
}
fmt.Printf("random int = %v\n", v)
s, err := generateString(10)
if err != nil {
log.Fatal(err)
}
fmt.Printf("random string = %v\n", s)
}
func generateInt(n int64) (int64, error) {
r, err := rand.Int(rand.Reader, big.NewInt(n))
if err != nil {
return 0, err
}
return r.Int64(), nil
}
func generateString(length int) (string, error) {
b := make([]byte, length)
_, err := rand.Read(b)
if err != nil {
return "", err
}
return base64.URLEncoding.EncodeToString(b), nil
}
