rows: clean up error handling

errors.go

@@ -17,6 +17,7 @@ import (
 )
 
 var (
+	errInvalidConn = errors.New("Invalid Connection")
 	errMalformPkt  = errors.New("Malformed Packet")
 	errNoTLS       = errors.New("TLS encryption requested but server does not support TLS")
 	errOldPassword = errors.New("It seems like you are using old_passwords, which is unsupported. See https://github.com/go-sql-driver/mysql/wiki/old_passwords")

rows.go

@@ -11,7 +11,6 @@ package mysql
 
 import (
 	"database/sql/driver"
-	"errors"
 	"io"
 )
 
@@ -44,7 +43,7 @@ func (rows *mysqlRows) Close() (err error) {
 	// Remove unread packets from stream
 	if !rows.eof {
 		if rows.mc == nil {
-			return errors.New("Invalid Connection")
+			return errInvalidConn
 		}
 
 		err = rows.mc.readUntilEOF()
@@ -53,17 +52,16 @@ func (rows *mysqlRows) Close() (err error) {
 	return
 }
 
-func (rows *mysqlRows) Next(dest []driver.Value) error {
+func (rows *mysqlRows) Next(dest []driver.Value) (err error) {
 	if rows.eof {
 		return io.EOF
 	}
 
 	if rows.mc == nil {
-		return errors.New("Invalid Connection")
+		return errInvalidConn
 	}
 
 	// Fetch next row from stream
-	var err error
 	if rows.binary {
 		err = rows.readBinaryRow(dest)
 	} else {