type Update struct

{ Name string `bson:"name"` Obj *StructB `bson:"obj,omitempty"` }

type StructB struct

{ A string `bson:"a"` }

update := Update

{ Name:"name", }

db.Update(filter,update)

error message ``"multiple write errors: [{write errors: [{'$set' is empty. You must specify a field like so: {$set:

{<field>: ...}

}}]},

{<nil>}

]"``