package main
import (
"regexp"
"fmt"
)
func main() {
var re = regexp.MustCompile(`(?m)^\S+\h+(\S+)\R\K(?:\S+\h+\1(?:\R|\Z))+`)
var str = `lineA 12345
lineB 12345
lineC 12345
lineD 788878
lineE 110881
lineF 110881
lineG 110881
lineH 287778
lineJ 251287
lineK 242424
lineL 242424
lineM 242424`
var substitution = ""
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/