EDIT: The resolution for this ticket is that we should document that unmarshalling into a struct that has a field with type interface{} yields a bson.D. This differs from mgo, which defaulted to bson.M.

if we have a struct like 

type Something struct {
   Val []interface `bson="val"`
}

In our case this struct is an array of objects. It was actually just a draftJS block. in JSON it would look like this, and this is what it would look like after being inserted into mongo

[{
  "entityRanges" : [ ],
  "inlineStyleRanges" : [ ],
  "key" : "fb86k",
  "text" : "",
  "type" : "unstyled"
}]

the mongo driver marshalled this perfectly into the database. No issues there. However when pulling the data out, we receive 

[
  {Key: "entityRanges", Value: [ ]},
  {Key: "inlineStyleRanges", Value: [ ]},
  {Key: "key", Value: "fb86k"},
  {Key: "type", Value: "unstyled"},

]

this doesn't reflect the data in the database and actually makes no sense why mongo decided to break up the object like this