Unable to fetch bulkwriteresult result upon update to mongoose 5

[arvi]

Do you want to request a feature or report a bug?
bug

What is the current behavior?
Upon updating to mongoose 5 from mongoose 4, bulkwriteresult object is unable to retrieve nMatched, nModified, etc. It is now undefined

If the current behavior is a bug, please provide the steps to reproduce.

          const bulkWriteResult = await Student.bulkWrite(
            [...bulkAddDeleteOps, ...bulkUpdateOps, ...bulkDeleteOps],
            { ordered: true, w: 1 },
            (err, result) => {
              if (err) throw err;
            },
          );

          // this used to work before package upgrade
          bulkWriteStatus = {
            matched: bulkWriteResult.nMatched,
            modified: bulkWriteResult.nModified,
            ok: bulkWriteResult.ok,
          };

// when I log `bulkWriteResult` in console, it shows this
 BulkWriteResult {
   result:
    { ok: 1,
      writeErrors: [],
      writeConcernErrors: [],
      insertedIds: [],
      nInserted: 0,
      nUpserted: 0,
      nMatched: 28,
      nModified: 28,
      nRemoved: 0,
      upserted: [] },
   insertedCount: 0,
   matchedCount: 28,
   modifiedCount: 28,
   deletedCount: 0,
   upsertedCount: 0,
   upsertedIds: {},
   insertedIds: {},
   n: 0 }

What is the expected behavior?
Work as-is the current version

Please mention your node.js, mongoose and MongoDB version.
node: 8.9.4
mongoose: 5.3.10
mongodb: 3.6.4

[vkarpov15]

We will need to make a note of these changes in the migration guide, but the new properties are documented here so you should either do .then(res => res.result) or use the new property names.