默认情况下，nginx.conf里没有server配置，用的是include指令引入了conf.d里的配置文件。最好是把server配置都放在conf.d里，当然在nginx.conf里写sever配置也允许，但这样就不太好管理了。默认应该是这样的：

http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
sendfile on;
#tcp_nopush on;
keepalive_timeout 65;
#gzip on;
include /etc/nginx/conf.d/*.conf;
}

nginx版本试过1.16.1和1.20.1

location ^~ /forum {
set $args mod=viewthread&${args};
rewrite ^(.*)$ /$uri last;
}