# Golang : Number guessing game with user input verification example

Helping a Golang student from Mexico. She is building a simple random number guessing game and she wants to know how to check the user input to determine if the user input is indeed an integer value.

Simple, use the `strconv.ParseInt()` to parse the user input and if the error != nil, then we know the user input is not integer

For example,

`````` userNumber, err := strconv.ParseInt(userInput, 10, 0)
if err != nil {
fmt.Println("You must enter an integer value.")
}
``````

The full program. Here you go!

`````` package main

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

var (
userInput string
attempts  int = 0
)

// https://www.socketloop.com/tutorials/golang-random-integer-with-rand-seed-within-a-given-range
func numRandom(min, max int) int {
rand.Seed(time.Now().Unix())
return rand.Intn(max-min) + min
}

func main() {
numberToGuess := numRandom(1, 10)
//fmt.Println(numberToGuess)

for {
attempts++
fmt.Println("A number is generated between 1 to 10. What do you think the number is: ")

// see https://www.socketloop.com/tutorials/golang-fix-fmt-scanf-on-windows-will-scan-input-twice-problem
// for scanf under Windows OS
fmt.Scanf("%v\n", &userInput)

// check if userinput is integer
userNumber, err := strconv.ParseInt(userInput, 10, 0)
if err != nil {
fmt.Println("You must enter an integer value.")
} else if numberToGuess == int(userNumber) {
break
} else if int(userNumber) < numberToGuess {
fmt.Printf("Smaller than the number. Try again\n")
} else {
fmt.Printf("Larger than the number. Try again\n")
}
}
fmt.Printf("Yup, the number is %v. You guessed it correctly after %v attempts\n", numberToGuess, attempts)

}
``````

Sample output:

A number is generated between 1 to 10. What do you think the number is:

2

Larger than the number. Try again

A number is generated between 1 to 10. What do you think the number is:

1

Yup, the number is 1. You guessed it correctly after 2 attempts

Happy coding!

References:

https://www.socketloop.com/tutorials/golang-fix-fmt-scanf-on-windows-will-scan-input-twice-problem

https://www.socketloop.com/tutorials/golang-random-integer-with-rand-seed-within-a-given-range

#### See also : Golang : Fix fmt.Scanf() on Windows will scan input twice problem

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