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.
- https://github.com/google/uuid/blob/master/version4.go#L29-L38
- https://github.com/google/uuid/blob/master/uuid.go#L36
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 }