How to replace nth char from a string in Go

Question

I want to replace the nth char in the original string. I can access the nth char from the string by using chars[i], but when I assign a value to chars[i], I get an error.

package main
import "fmt"

func main() {
  var chars = "abcdef"
  fmt.Println(string(chars[3]))
  chars[3] = "z" // is not working
}

Answer 1

Strings are immutable.

chars = chars[:3] + "z" + chars[4:]

Answer 2

This is happening because chars is actually a string and is immutable. If you declared it appropriately (as a byte slice) then you can assign to it as you're attempting. Here's an example;

package main
import "fmt"

func main() {
  var chars = []byte{'a', 'b', 'c', 'd', 'e', 'f'}
  fmt.Println(string(chars[3]))
  fmt.Printf("%T\n", chars)
  chars[3] = 'z'
  fmt.Println(string(chars))
}

https://play.golang.org/p/N1sSsfIBQY

Alternately you could use reslicing as demonstrated in the other answer.