Configuring X-Forwarded-For Header in GKE nginx Proxy Configuration

Question

I have installed an nginx controller in GKE (GCP) on a cluster and a rails app set up with a Rack Attack configuration for restricting access. We're having trouble getting the remote IP address of incoming requests. It keeps returning the ingress IP not the remote user's IP. I've found several mentions of this issue in various forms. It mentions adding a setting to the nginx proxy config. Having installed the nginx controller using the standard public files on github, I don't know how to reconfigure the proxy on this controller. How would I apply a new proxy config to this setup?

See ingress controller yaml below:

apiVersion: v1
kind: Service
metadata:
  creationTimestamp: "2020-04-30T15:45:32Z"
  labels:
    app: nginx-ingress
    chart: nginx-ingress-1.36.3
    component: controller
    heritage: Tiller
    release: nginx-ingress
  name: nginx-ingress-controller
  namespace: nginx-ingress
  resourceVersion: "113532709"
  selfLink: /api/v1/namespaces/nginx-ingress/services/nginx-ingress-controller
  uid: a045e8e8-8af9-11ea-8a88-42010a030a07
spec:
  clusterIP: 10.163.8.100
  externalTrafficPolicy: Cluster
  ports:
  - name: http
    nodePort: 30487
    port: 80
    protocol: TCP
    targetPort: http
  - name: https
    nodePort: 32616
    port: 443
    protocol: TCP
    targetPort: https
  selector:
    app: nginx-ingress
    app.kubernetes.io/component: controller
    release: nginx-ingress
  sessionAffinity: None
  type: LoadBalancer
status:
  loadBalancer:
    ingress:
    - ip: x.x.x.x