package main

import (
    "fmt"
    "regexp"
)

const sample = `darted`

func main() {
    var re = regexp.MustCompile(`^(.*?)d(.*)$`)
    s := re.ReplaceAllString(sample, `$1c$2`)
    fmt.Println(s)//prints 'arted' expected: carted
}

Go playground: https://go.dev/play/p/-f0Cd_81eMX

Trying a non-alpha characters works (i.e. ‘$1.$2’ results in ‘.arted’)

Adding more than one alpha character works (i.e. ‘$1cl$2’ results in ‘clarted’)

Why doesn’t the above sample work?

Can someone show me what I’m doing wrong, or confirm this is a bug in Go that needs to be reported?

>Solution :

In your replacement:

`$1c$2`

This is as interpreted as a capture group literally named $1c which doesn’t exist in the regex. You want ${1}c.