code: func NewBitFieldDescriptor(nullable NullableColumn, metadata []byte) (
  	fd FieldDescriptor,
  	remaining []byte,
  	err error) {
  
  	if len(metadata) < 2 {
  		return nil, nil, errors.New("Metadata has too few bytes")
  	}
  
  	return &bitFieldDescriptor{
  		baseFieldDescriptor: baseFieldDescriptor{
  			fieldType:  mysql_proto.FieldType_BIT,
  			isNullable: nullable,
  		},
  		numBits: ((uint16(metadata[0]) * 8) + uint16(metadata[1])),
  	}, metadata[2:], nil
  }
docs: // This returns a field descriptor for FieldType_BIT (i.e., Field_bit_as_char)