code: func (d *Database) Placeholders(src interface{}, includePk bool) ([]string, error) {
  	data, err := getFields(reflect.TypeOf(src))
  	if err != nil {
  		return nil, err
  	}
  
  	var placeholders []string
  	for _, name := range data.columns {
  		if !includePk && name == data.pk {
  			continue
  		}
  		ph := d.placeholder(len(placeholders) + 1)
  		placeholders = append(placeholders, ph)
  	}
  
  	return placeholders, nil
  }
docs: // Placeholders returns a list of placeholders suitable for an INSERT or UPDATE query.
  // If includePk is false, the primary key field is omitted.