Add field type JSON support

const.go

@@ -107,7 +107,8 @@ const (
 	fieldTypeBit
 )
 const (
-	fieldTypeNewDecimal byte = iota + 0xf6
+	fieldTypeJSON byte = iota + 0xf5
+	fieldTypeNewDecimal
 	fieldTypeEnum
 	fieldTypeSet
 	fieldTypeTinyBLOB

packets.go

@@ -1106,7 +1106,7 @@ func (rows *binaryRows) readRow(dest []driver.Value) error {
 		case fieldTypeDecimal, fieldTypeNewDecimal, fieldTypeVarChar,
 			fieldTypeBit, fieldTypeEnum, fieldTypeSet, fieldTypeTinyBLOB,
 			fieldTypeMediumBLOB, fieldTypeLongBLOB, fieldTypeBLOB,
-			fieldTypeVarString, fieldTypeString, fieldTypeGeometry:
+			fieldTypeVarString, fieldTypeString, fieldTypeGeometry, fieldTypeJSON:
 			var isNull bool
 			var n int
 			dest[i], isNull, n, err = readLengthEncodedString(data[pos:])