package main

import (
    "regexp"
    "fmt"
)

func main(){
	var re = regexp.MustCompile(`(?m)^/(?:[id]|na|fm)/([^/\s]*/\d{4}/\d{2}/\d{2}/\S*?)(?:/,|[^_]+_)640(?:\D|$)`)
    var str = `/i/int/2021/11/18/019e1691-614c-4402-a8c1-d0239ad1ac45/,640-1_999899,480-1_999899,960-1_999899,1280-1_999899,1920-1_999899,.mp4.csmil/master.m3u8?set-segment-duration=responsive

/i/int/2021/11/25/,live_20211125_215206_sendeton_640x360-50p-1200kbit,live_20211125_215206_sendeton_480x270-50p-700kbit,live_20211125_215206_sendeton_960x540-50p-1600kbit,live_20211125_215206_sendeton_1280x720-50p-3200kbit,live_20211125_215206_sendeton_1920x1080-50p-5000kbit,.mp4.csmil/master.m3u8

/i/int/2021/11/18/019e1691-614c-4402-a8c1-d0239ad1ac45/,640
/i/int/2021/11/25/,live_20211125_215206_sendeton_640`
    
    for _, match := range re.FindAllStringSubmatch(str, -1) {
        fmt.Println(match[1])
    }
}