code: func NewTimestampFieldDescriptor(nullable NullableColumn) FieldDescriptor {
  	return newFixedLengthFieldDescriptor(
  		mysql_proto.FieldType_TIMESTAMP,
  		nullable,
  		4,
  		func(b []byte) interface{} {
  			return time.Unix(int64(LittleEndian.Uint32(b)), 0).UTC()
  		})
  }
docs: // This returns a fields descriptor for FieldType_TIMESTAMP
  // (i.e., Field_timestamp)