Istio Virtual service dark launch (deployment) Header exact not working

Question

Currently i have an architecture where my API Gateway (http) is exposed to users and i have many internal services (gRPC) running. So the user request propagate as API Gateway (http) --> users service (gRPC). I am running two pods for users service ( v1 and v2) in AWS EKS.

I want to do a dark launch where istio will forward request to users-v2 pod only if the request has 'x-testing = tester' header value.

i have some questions, i believe the http headers will propagate from API gateway to users service.

Below are my configs

Deployments

apiVersion: apps/v1
kind: Deployment
metadata:
  name: users-v2
  labels:
    app: users
    version: v2
spec:
  replicas: 1
  selector:
    matchLabels:
      app: users
      version: v2
  template:
    metadata:
      labels:
        app: users
        version: v2
    spec:
      serviceAccountName: kappa-users
      containers:
        - name: users
          image: users:0.0.1
          imagePullPolicy: IfNotPresent
          ports:
            - containerPort: 9090
          env:
          - name: USERS_PORT
            value: '9090' 

Virtual service

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: users
spec:
  hosts:
  - users
  http:
  - match:
    - headers:
        x-testing:
          exact: tester
    route:
    - destination:
        host: users
        subset: v2
  - route:
    - destination:
        host: users
        subset: v1

Destination Rule

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: users
spec:
  host: users
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2    

Can you please help me

Thanks,