func NewRandomGenerater(r *rand.Rand, len int) RandomGenerater {
	return &randomGeneraterImpl{
		r:   r,
		len: len,
	}
}
NewRandomGenerater new generater
package util
import (
	"math/rand"
)
type RandomGenerater interface {
	RandomString() string
}
type randomGeneraterImpl struct {
	r   *rand.Rand
	len int
}