random use crypto/rand instead of math/rand 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16package main import ( "crypto/rand" "fmt" "math/big" ) var randIntn = func(n int64) int64 { num, _ := rand.Int(rand.Reader, big.NewInt(n)) return num.Int64() } func main() { fmt.Println(randIntn(10000)) }