How do I add a request header to an endpoint in ngrok.yml file?

Ngrok v3 is deprecating tunnels in the ngrok.yml file in favour of endpoints: https://ngrok.com/docs/agent/config/v3/#endpoint-configurations

I have a tunnel configured like this:

tunnels:
  mytunnel:
    proto: http
    addr: 3000
    host_header: localhost

The host_header is the important bit.

I have tried translating this in to an endpoint but cannot work out how to add the host header.

Without the host header it looks like:

endpoints:
  - name: myendpoint
    upstream:
      url: 3000

This works but lacks the host header.

From the documentation, it looks like I want to use request_header.add.

However, I cannot workout from the documentation where that should go in the config. Wherever I try to place it, I get errors along the lines of:

ERROR:  Error reading configuration file 'ngrok/ngrok.yml':YAML parsing error: yaml: unmarshal errors:
ERROR:    line 7: field request_header not found in type config.Endpoint

Can anyone guide me to the correct configuration here?

Yeah, this isn't very well documented. We're transitioning to configuring endpoints with traffic_policy. So, until we fix our docs, I'll explain what you need to do here. To add a request header, you would configure an inbound action of type: "add-headers". The config would look something like the following:

version: 3
endpoints:
  - name: myendpoint
    upstream:
      url: 3000
    traffic_policy: 
      inbound:
        - actions:
          - type: "add-headers"
            config:
              headers:
                host: localhost