gobuster dir -u http://localhost:8000 -w list.txt -H 'Host: sdf'

sudo tcpdump -i lo -nn -A port 8000 | grep Host
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 262144 bytes
Host: localhost:8000
Host: localhost:8000
Host: localhost:8000
Host: localhost:8000
Host: localhost:8000
Host: localhost:8000
Host: localhost:8000