what is the password of docker image user gopher?

[QGB]

$ id
uid=1000(gop: not found00(gopher) groups=1000(gopher)
$
$ su
Password:
su: Authentication failure

[QGB]

docker exec -it -u 0 5620f2347391 bash


root@5620f2347391:/examples# cat /etc/shadow
root:*:17728:0:99999:7:::
daemon:*:17728:0:99999:7:::
bin:*:17728:0:99999:7:::
sys:*:17728:0:99999:7:::
sync:*:17728:0:99999:7:::
games:*:17728:0:99999:7:::
man:*:17728:0:99999:7:::
lp:*:17728:0:99999:7:::
mail:*:17728:0:99999:7:::
news:*:17728:0:99999:7:::
uucp:*:17728:0:99999:7:::
proxy:*:17728:0:99999:7:::
www-data:*:17728:0:99999:7:::
backup:*:17728:0:99999:7:::
list:*:17728:0:99999:7:::
irc:*:17728:0:99999:7:::
gnats:*:17728:0:99999:7:::
nobody:*:17728:0:99999:7:::
_apt:*:17728:0:99999:7:::
messagebus:*:17945:0:99999:7:::
gopher:*:17945:0:99999:7:::