doc: fix spelling error
@@ -184,7 +184,7 @@ However, we can expose a http or https service using frp.
5. Send dns query request by dig:
- `dig @x.x.x.x -p 6000 www.goolge.com`
+ `dig @x.x.x.x -p 6000 www.google.com`
### Forward unix domain socket
