Detailed steps to reproduce the problem?

1. Create a document that both key and value are strings, but the key is "$date".

   bson.D{{"$date", "2024-05-20T23:59:59Z"}}
   

2. Marshaling the object to canonical extended JSON succeeds

   bson.MarshalExtJSON(doc, true, false)
   

3. Unmarshaling the JSON back to BSON

   bson.UnmarshalExtJSON(jsonBytes, true, meta)
   

   It returns an error.

   invalid JSON input; expected {
   

Definition of done: what must be done to consider the task complete?

We expect that marshaling from BSON to canonical extended JSON is reversible through unmarshaling using the go driver. If marshaling succeeds, unmarshaling should produce the original BSON document without an error. Mongodump and mongorestore rely on this assumption to perform database backups correctly.

The exact Go version used, with patch level:

1.21

The exact version of the Go driver used:

v1.11.9