You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: example_test.go
    path of file: ./repos/go-cloud/docstore/mongodocstore
    
    the code of the file until where you have to start completion: // Copyright 2019 The Go Cloud Development Kit Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law
    
func Example_openCollectionFromURL() {
	// PRAGMA: This example is used on gocloud.dev; PRAGMA comments adjust how it is shown and can be ignored.
	// PRAGMA: On gocloud.dev, add a blank import: _ "gocloud.dev/docstore/mongodocstore"
	// PRAGMA: On gocloud.dev, hide lines until the next blank line.
	ctx := context.Background()

	// docstore.OpenCollection creates a *docstore.Collection from a URL.
	coll, err := docstore.OpenCollection(ctx, "mongo://my-db/my-collection?id_field=userID")
	if err != nil {
		log.Fatal(err)
	}
	defer coll.Close()
}