Project 11: Password generator

Complete video course: Udemy

Introduction

A password generator is a program that generates a strong random password (containing uppercase and lowercase characters, and numbers).

In our case, the generated password will be 8 characters long. The result will be displayed to the user upon generation.

Practical

Boilerplate code:

package main

import (

)

func main() {

}

We start by importing packages that we need for our program:

import (
    "fmt"
    "math/rand"
    "time"
)

The fmt package is for the output operation (displaying the password to the user), and the math/rand and time packages are for the pseudo-random selection that we shall do to generate a random password.

Next, we shall create a constant (an identifier whose value cannot be changed once set) which contains the pool of characters from which we shall generate our password. We are using a constant instead of a variable since we will not update this data at any point in the program. It is also a good practice to have constants outside any functions, so we define it before the main function:

const pool = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

Note that we use the const keyword with constants and not var which is for variables.

In our main function now, we start by defining a variable containing the desired password length (8), and declaring another one where we will store the generated password:

password_length := 8
var password string

Now it’s time to generate the password. First, we set the seed to the current time in nanoseconds to make this even more random:

rand.Seed(time.Now().UnixNano())

Next, we use a for loop to perform a random selection from our pool of characters n times, where n is the desired password length:

for i := 0; i < password_length; i++ {
    character := pool[rand.Intn(len(pool))]
    password += string(character)
}

To access the nth element in a collection, we use indices that define the position (and start from 0). In our case, we therefore pass as the index value a random number in the range 0 - 7 (rand.Intn(len(pool)). Once we have the character at that position, we append it to the password variable using the add and assign operator (+=).

Note that we use string(character). This is because, in the previous line, we get back a rune that is a special data type in Go. We cannot add a rune to a string hence the string conversion first.

Once the loop is complete, we can display the generated password to the user:

fmt.Println("Generated password is: ", password)

Complete code:

package main

import (
   "fmt"
   "math/rand"
   "time"
)

const pool = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

func main() {
   password_length := 8
   var password string
  
   rand.Seed(time.Now().UnixNano())
   for i := 0; i < password_length; i++ {
      character := pool[rand.Intn(len(pool))]
      password += string(character)
   }
  
   fmt.Println("Generated password is: ", password)
}

Next: Project 12: JSON parser