title: docker container has no access to localhost webhook
body: <p>I'm working on our webhook locally before building a docker container, and want my (Linux) container to communicate with it, using <code>host.docker.internal:ping</code>.<br>
  It had been working before, but lately, for some reason, I'm getting this error from our <code>graphql-engine</code>, Hasura:  </p>
  
  <pre><code>    { 
     "timestamp":"2019-11-05T18:45:32.860+0000",
     "level":"error",
     "type":"webhook-log",
     "detail":{ 
        "response":null,
        "url":"http://host.docker.internal:3000/simple/webhook",
        "method":"GET",
        "http_error":{ 
           "type":"http_exception",
           "message":"ConnectionFailure Network.Socket.getAddrInfo (called with preferred socket type/protocol: AddrInfo {addrFlags = [AI_ADDRCONFIG], addrFamily = AF_UNSPEC, addrSocketType = Stream, addrProtocol = 0, addrAddress = &lt;assumed to be undefined&gt;, addrCanonName = &lt;assumed to be undefined&gt;}, host name: Just \"host.docker.internal\", service name: Just \"3000\"): does not exist (Temporary failure in name resolution)"
        },
        "status_code":null
     }
  }   
  </code></pre>
  
  <p>Here's my docker compose:  </p>
  
  <pre><code>version: '3.6'
  
  services:
  
    postgres:  
      image: postgres:11.2  
      restart: always  
      ports:  
        - 5432:5432  
      volumes:  
        - postgres:/var/lib/postgresql/data  
      environment:  
        - POSTGRES_DB=postgres  
        - POSTGRES_USER=...  
        - POSTGRES_PASSWORD=...  
  
    graphql-engine:  
      image: hasura/graphql-engine:latest  
      depends_on:  
        - postgres  
      restart: always  
      environment:  
        - HASURA_GRAPHQL_DATABASE_URL=postgres://...:...@postgres:5432/postgres  
        - HASURA_GRAPHQL_ACCESS_KEY=...  
        - HASURA_GRAPHQL_AUTH_HOOK=http://host.docker.internal:3000/simple/webhook  
      command:  
        - graphql-engine  
        - serve  
        - --enable-console  
      ports:  
        - 8080:8080  
         volumes:   
    postgres:   
    data:
  </code></pre>
  
  <p>The local project is for sure working and listening to port 3000. Nontheless, it isn't receiving any requests [as it should] from the graphql-engine container. Could it be related to our proxy?</p>