buildMutation not working properly with header

[cristal2431]

I'm trying to use buildMutation, and it doesn't seem to be working correctly. I'm also confused by the discrepancy between docs and source.

I have below code:

 await (async () => {
        const result = await client.mutate(
          buildMutation(
            client,
            gql(createToDo),
            {
              input: [gql(createToDoInput)],
              variables: {
                input: selectedToDo
              },
              context: {
                headers: {
                  'Content-Type': 'application/graphql',
                  'X-Appsync-Domain': environment.domain,
                }
              }
            },
            _variables => [gql(listToDo)],
            'ToDo'
          )
        )
      });

I am passing x-appsync-domain, as I am connecting through DNS as mentioned in this blog: https://aws.amazon.com/blogs/mobile/introducing-private-apis-on-aws-appsync/

However, in the request header is not being passed.