Overview

Runtime error in the program can happen in the below cases. All the below cases will also create a panic

• Out of bounds array access

• Calling a function on a nil pointer

• Sending on a closed channel

• Incorrect type assertion

Example

Let’s see an example of runtime error caused by out of bounds array access.

package main

import "fmt"

func main() {

	a := []string{"a", "b"}
	print(a, 2)
}

func print(a []string, index int) {
	fmt.Println(a[index])
}

Output

panic: runtime error: index out of range [2] with length 2

goroutine 1 [running]:
main.checkAndPrint(...)
        main.go:12
main.main()
        /main.go:8 +0x1b
exit status 2

In the above program, we have a slice of length 2 and we are trying to access slice at index 2 in the print function. Out of bound access is not allowed and it will create panic as seen from the output. Notice that in the output there are two things

• The error message

• Stack trace of where the panic happened

There are many more cases in which runtime error can happen in a program. We are not going to mention all of them but you get the idea