Unexpected token' when recursively calling async function in Nodejs

Question

My app contains posts with nested comments in Firebase Firestore structured such that each post/comment with docID has a sub collection postComments. Thus, a given post/comment can have an infinite number of nested comments.

comments
 - docID
   postComments
    - docID
    - docID
    - docID
 - docID
   postComments
    - docID
    - docID

I am currently writing a Firebase cloud function to recursively query all documents and sub collection documents of a given docID and return all of those documents in an array. My plan was to define the getChildComments async function which takes in a docID and returns all of the documents in that document's postComments sub collection. I would then recursively call getChildComments until I have built an array with all of the nested comments in a thread.

exports.loadWholeCommentThread = functions.https.onCall(async (data, context) => {
       let comments = await getChildComments(data.rootID);
       return comments;
});

async function getChildComments(docID) {
  try {
     const db = admin.firestore();
     const commentsRef = db.collection('comments').doc(docID).collection('postComments');
     var comments = [];
     const commentsQuerySnap = await commentsRef.get();

     commentsQuerySnap.forEach((comment) => {
       let commentData = comment.data();
       comments.push(commentData);
       if (commentData.commentCount > 0) {
         let childComments = await getChildComments(commentData.commentID);
         comments.concat(childComments);
       }
     });

     return comments;
  } catch (error) {
     functions.logger.log(error);
     throw new functions.https.HttpsError('unknown', 'ERROR0', { message: error.message } )
  }
}

Unfortunately, when I try to deploy my code, I get the error Parsing error. Unexpected token getChildComments on the line where I recursively call getChildComments inside of getChildComments. Removing the await from this line fixes the build issue but then the recursive call doesn't finish.

How should I fix my issue? Or is there a better way to query all nested documents?