package main
import (
"regexp"
"fmt"
)
func main() {
var re = regexp.MustCompile(`<\s*\/?\s*img(?![^>]*class=)`)
var str = `<img src="https://google.com/animage.jpg" class="google"><img src="https://yahoo.com/animage.jpg"><img src="https://google.com/animage.jpg" class="google"><img src="https://google.com/animage.jpg" class="google"><img src="https://yahoo.com/animage.jpg"><img src="https://yahoo.com/animage.jpg"><img src="https://yahoo.com/animage.jpg">`
var substitution = "$0 class="whatever""
fmt.Println(re.ReplaceAllString(str, substitution))
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Golang, please visit: https://golang.org/pkg/regexp/