func findOne(coll *mongo.Collection, t *testing.T) {
ss := &smallStruct{PER_TRIAL / 2}
obj, err := mongo.Marshal(ss)
if err != nil {
t.Errorf("findOne Marshal: %v\n", err)
}
for i := 0; i < PER_TRIAL; i++ {
_, err = coll.FindOne(obj)
if err != nil {
t.Errorf("findOne FindOne: %v\n", err)
}
}
}
