code: func (c *Criterion) In(values ...interface{}) *Query {
  	c.operator = in
  	c.inValues = values
  
  	q := c.query
  	q.fieldCriteria[q.currentField] = append(q.fieldCriteria[q.currentField], c)
  
  	return q
  }
docs: // In test if the current field is a member of the slice of values passed in