Dgraph's ratel and alpha can be ingress with prefix?

I want to deploy dgraph with k8s and ingress ratel and alpha with some prefix.
But the default ingress’s path is /.
Can i do this?

I defined the following configuration file, but It does not work.
Then [Launch Offline] button is always https://192.168.1.118:30443/?local.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: helmet-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$2
    nginx.ingress.kubernetes.io/proxy-redirect-from: /
    nginx.ingress.kubernetes.io/proxy-redirect-to: $location_path/
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/service-upstream: "true"
    nginx.ingress.kubernetes.io/proxy-body-size: "0"
    nginx.ingress.kubernetes.io/proxy-read-timeout: "600"
    nginx.ingress.kubernetes.io/proxy-send-timeout: "600"
spec:
  rules:
  - http:
      paths:
      - path: /helmet/ratel(/|$)(.*)
        backend:
          serviceName: dgraph-ratel
          servicePort: 80
      - path: /helmet/alpha(/|$)(.*)
        backend:
          serviceName: dgraph-alpha
          servicePort: 8080

I access dgraph with https://192.168.1.118:30443/helmet/ratel?local by manual.
It works very well.