How to set up an ingress or node so that the express webserver does not know which way it is being proxied?

Question

Node.js

spoiler

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - http:
      paths:
        - path: /mywebapi
          backend:
            serviceName: mywebapi-service
            servicePort: 80

doesn't work like that

spoiler

app.get('/', (req, res) => res.send('ok'));

that's how it works

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app.get('/mywebapi', (req, res) => res.send('ok'));

How to set up an ingres or a node so that it does not know at all which way it is being proxied?