download only 30 seconds audio of youtube video with youtube-dl code example

Example: youtube-dl download part of video

## Manually
# Retrieve the two URLs
youtube-dl -g https://www.youtube.com/watch?v=gESHIrvIQQo
# The first URL
video_url="https://r3---sn-mv-cvne.googlevideo.com/videoplayback/id/80448722bbc8410a/itag/298/source/youtube/requiressl/yes/pl/23/ei/5wCfWY6dBeOj8gSSxZaACQ/mv/m/initcwndbps/5055000/ms/au/mm/31/mn/sn-mv-cvne/ratebypass/yes/mime/video%2Fmp4/otfp/1/gir/yes/clen/5231968228/lmt/1502479662079137/dur/18575.164/key/dg_yt0/beids/%5B9466591%5D/mt/1503592562/signature/8CCFBF5CAB97341D0CB1F34E85AB6EE20FC7A03E.7679F39A8603CF41A95F10232E2A921EB0774101/ip/206.34.122.70/ipbits/0/expire/1503614279/sparams/ip,ipbits,expire,id,itag,source,requiressl,pl,ei,mv,initcwndbps,ms,mm,mn,ratebypass,mime,otfp,gir,clen,lmt,dur/"
# The second URL
audio_url="https://r3---sn-mv-cvne.googlevideo.com/videoplayback/id/80448722bbc8410a/itag/140/source/youtube/requiressl/yes/pl/23/ei/5wCfWY6dBeOj8gSSxZaACQ/mv/m/initcwndbps/5055000/ms/au/mm/31/mn/sn-mv-cvne/ratebypass/yes/mime/audio%2Fmp4/otfp/1/gir/yes/clen/295235970/lmt/1502480001536214/dur/18575.243/key/dg_yt0/beids/%5B9466591%5D/mt/1503592562/signature/4AACC8E27F9036D36D4D623A771A9F2BAC4674BA.7E4F4FB4DC023E3FE491A991F0F9F2329648DE9D/ip/206.34.122.70/ipbits/0/expire/1503614279/sparams/ip,ipbits,expire,id,itag,source,requiressl,pl,ei,mv,initcwndbps,ms,mm,mn,ratebypass,mime,otfp,gir,clen,lmt,dur/"
ffmpeg -ss 42:30 -i "$video_url" -ss 42:30 -i "$audio_url" -to 49:10 -map 0:v -map 1:a -c copy gog-vs-triv.mkv
## Single line
ffmpeg $(youtube-dl -g 'https://www.youtube.com/watch?v=oHg5SJYRHA0' | sed "s/.*/-ss 00:05 -i &/") -to 01:00 -c copy out.mkv