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How to Get Int31n Type Random Number in Golang?
• Last Updated : 26 Mar, 2020

Go language provides inbuilt support for generating random numbers of the specified type with the help of a math/rand package. This package implements pseudo-random number generators. These random numbers are generated by a source and this source produces a deterministic sequence of values every time when the program run. And if you want to random numbers for security-sensitive work, then use the crypto/rand package.
You are allowed to generate a non-negative pseudo-random number in [0, n) of 31-bit integer n as an int32 type from the default source with the help of the Int31n() function provided by the math/rand package. So, you need to add a math/rand package in your program with the help of the import keyword to access the Int31() function. This method will panic if the value of n is <= 0.

Syntax:

`func Int31n(n int32) int32`

Let us discuss this concept with the help of the given examples:

Example 1:

 `// Golang program to illustrate``// how to get a random number``package main`` ` `import (``    ``"fmt"``    ``"math/rand"``)`` ` `// Main function``func main() {`` ` `    ``// Finding random numbers of int31n type``    ``// Using Int31n() function``    ``res_1 := ``rand``.Int31n(2)``    ``res_2 := ``rand``.Int31n(4)``    ``res_3 := ``rand``.Int31n(1)`` ` `    ``// Displaying the result``    ``fmt.Println(``"Random Number 1: "``, res_1)``    ``fmt.Println(``"Random Number 2: "``, res_2)``    ``fmt.Println(``"Random Number 3: "``, res_3)``}`

Output:

```Random Number 1:  1
Random Number 2:  3
Random Number 3:  0
```

Example 2:

 `// Golang program to illustrate``// how to get a random number``package main`` ` `import (``    ``"fmt"``    ``"math/rand"``)`` ` `// Main function``func main() {`` ` `    ``// If the value of this function``    ``// is 0 or less than zero``    ``// the this method will panics``    ``res_1 := ``rand``.Int31n(0)``    ``res_2 := ``rand``.Int31n(-1)`` ` `    ``// Displaying the result``    ``fmt.Println(``"Random Number 1: "``, res_1)``    ``fmt.Println(``"Random Number 2: "``, res_2)`` ` `}`

Output:

panic: invalid argument to Int31n

goroutine 1 [running]:
math/rand.(*Rand).Int31n(0x43e280, 0x0, 0x43e280, 0x460000)
/usr/local/go/src/math/rand/rand.go:128 +0x180
math/rand.Int31n(…)
/usr/local/go/src/math/rand/rand.go:324
main.main()
/tmp/sandbox269134149/prog.go:16 +0x40

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