package main

import (
	"encoding/binary"
	"fmt"
	"math/rand"
	"os"
	"path/filepath"
	"strconv"
)

var MAX = 90
var MIN = 0

// Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n)
// from the default Source.
// It panics if n <= 0.
func random(min, max int) int {
	return rand.Intn(max-min) + min
}

func main() {
	var LENGTH int64 = 10
	if len(os.Args) != 2 {
		fmt.Printf("usage: %s length\n", filepath.Base(os.Args[0]))
		//os.Exit(1)
		fmt.Printf("Default length is %d\n", LENGTH)
	} else {
		LENGTH, _ = strconv.ParseInt(os.Args[1], 10, 64)
	}

	f, _ := os.Open("/dev/random")
	var seed int64

	_ = binary.Read(f, binary.LittleEndian, &seed)
	_ = f.Close()

	rand.Seed(seed)
	fmt.Println("Seed:", seed)

    GenPass(LENGTH)
}

// Read reads structured binary data from r into data. 
// Data must be a pointer to a fixed-size value or a slice of fixed-size values. 
// Bytes read from r are decoded using the specified byte order and written to successive fields of the data. 
// When decoding boolean values, a zero byte is decoded as false, and any other non-zero byte is decoded as true.

func GenPass(LENGTH int64) {
	startChar := "!"
	var i int64
	for i = 0; i < LENGTH; i++ {
		anInt := random(MIN, MAX)
		newChar := string(startChar[0] + byte(anInt))
		if newChar == " " {
			i = i - i
			continue
		}
		fmt.Print(newChar)
	}
	fmt.Println()
}

newChar := string(startChar[0] + byte(anInt))

$ go run goodPass.go 1
Seed: -5195038511418503382
b

$ go run goodPass.go 10
Seed: 8492864627151568776
k43Ve`+YD)

$ go run goodPass.go 50
Seed: -4276736612056007162
!=Gy+;XV>6eviuR=ST\u:Mk4Q875Y4YZiZhq&q_4Ih/]''`2:x