Replace lines that start with a prefix in a file

replaceLines.go

func replaceImageInTemplate(filepath string, prefix string, newString string) error {
	input, err := ioutil.ReadFile(filepath)
	if err != nil {
		return err
	}

    r, err := regexp.Compile(fmt.Sprintf("(?m)^%s(.*?)$", prefix))
	if err != nil {
		return err
	}

	newFile := r.ReplaceAll(input, []byte(newString))

	if err = ioutil.WriteFile(filepath, newFile, 0666); err != nil {
		return err
	}

	return nil
}