The "fully runnable example" from the Find Multiple Documents usage example page declares the results slice that is passed to `cursor.All` as

var results []bson.M

Despite the Go driver API documentation for `cursor.All` saying that the referenced slice will be "completely overwritten", in the case of no results, `results` will remain in an uninitialized state, which will be encoded as `null` in json (and bson). In contrast, if the results slice is declared as

var results []bson.M = make([]bson.M, 0, 0)
// or, equivalently
results := make([]bson.M, 0, 0)

in the case of no results, `results` will be fully initialized, and will be encoded as `[]` (the empty array) in json.

I am not sure whether this difference in behavior for the empty result set is intentional or avoidable. If it is intentional, then I think we may want to update our documentation to point out this gotcha more clearly (both in driver API docs and the examples page) and/or update our example to use the fully initialized results declaration, so that users who are relying on a consistent data structure, e.g., for returning the response in json format via a REST API, aren't led into this pitfall.