Use 4-byte UTF-8 by default (#979)

* Use 4-byte UTF-8 by default

* update comment

---------

Co-authored-by: lance6716 <lance6716@gmail.com>

Author: dveeden

client/auth.go

@@ -275,7 +275,7 @@ func (c *Conn) writeAuthHandshake() error {
 	data[11] = 0x00
 
 	// Charset [1 byte]
-	// use default collation id 33 here, is `utf8mb3_general_ci`
+	// use default collation id 255 here, is `utf8mb4_0900_ai_ci`
 	collationName := c.collation
 	if len(collationName) == 0 {
 		collationName = DEFAULT_COLLATION_NAME

mysql/const.go

@@ -183,10 +183,10 @@ const (
 	DEFAULT_IPV6_ADDR             = "[::1]:3306"
 	DEFAULT_USER                  = "root"
 	DEFAULT_PASSWORD              = ""
-	DEFAULT_FLAVOR                = "mysql"
-	DEFAULT_CHARSET               = "utf8"
-	DEFAULT_COLLATION_ID   uint8  = 33
-	DEFAULT_COLLATION_NAME string = "utf8_general_ci"
+	DEFAULT_FLAVOR                = MySQLFlavor
+	DEFAULT_CHARSET               = "utf8mb4"
+	DEFAULT_COLLATION_ID   uint8  = 255
+	DEFAULT_COLLATION_NAME string = "utf8mb4_0900_ai_ci"
 )
 
 const (