ingress-nginx to expose can not expose tidb dashboard

Accroding this configuration, still not worked, we got 504 gateway timeout.

ref: https://asktug.com/t/topic/1011985

```
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: lqb-yz-dashboard
namespace: tidb
spec:
rules:
- host: "lqb.mytest.org"
http:
paths:
- path: "/dashboard"
pathType: Prefix
backend:
service:
name: lqb-discovery
port:
number: 10262
```

I also have refer this page, but still not worked for me

ref: https://docs.pingcap.com/tidb-in-kubernetes/stable/access-dashboard

```
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: access-dashboard
namespace: ${namespace}
spec:
rules:
- host: ${host}
http:
paths:
- backend:
serviceName: ${SERVICE_NAME}
servicePort: ${PORT}
path: ${HTTP_PATH}
```

Is there have any idea?