void mongoc_client_destroy (mongoc_client_t *client);
Release all resources associated with
client and free the structure. Does nothing if
client is NULL.
Only call mongoc_client_destroy() on a single-threaded client. Do not call on a mongoc_client_t obtained from a mongoc_client_pool_t, which should instead be pushed back with mongoc_client_pool_push().
client: A mongoc_client_t.