Overview

In GO string are UTF-8 encoded. strings package of GO provides an Index method that can be used to get the index of the first occurrence of a substring in a particular string. It returns -1 is the substring is not present in the given string.

Below is the signature of the function

func Index(s, substr string) int 

Let’s look at the working code

Code:

package main

import (
    "fmt"
    "strings"
)

func main() {
    //Output will be 1 as "bc" is present in "abcdef" at index 1
    res := strings.Index("abcdef", "bc")
    fmt.Println(res)

    //Output will be 2 as "cd" is present in "abcdefabcdef" at index 2
    res = strings.Index("abcdefabcdef", "cd")
    fmt.Println(res)

    //Output will be -1 as "ba" is not present in "abcdef"
    res = strings.Index("abcdef", "ba")
    fmt.Println(res)
}

Output:

1
2
-1