使用Golang更新Firestore中的地图

I have a usecase where I need to clear a child element and all children from a document in firebase.

RootLevel.ObjectToClear

Object to clear has a bunch of different data types in it (int, float64, string, map[string]customStruct)

I tried by just creating a blank "object to clear" and overwriting it.

emptyObject := objectToClear{}
rootObject.objectToClear = emptyObject

That seemed to work fine for everything except the map[string]customStruct. I even tried to do an explicit delete of every key in the map and that didn't work either.

for k := range rootObject.objectToClear.MyMap {
    delete(rootObject.objectToClear.MyMap, k)
}

If it matters, when I am merging I am using the "MergeAll" function.

firestorehelper.MergeAll(path, workoutMap)

Clearly I am missing something about how the MAP interaction is working but I am not sure what. Any help would be much appreciated.