Add default port for mysql connections (#13)

The pq driver already supports this natively, but the mysql driver does not. This commit adds a default port 3306 for mysql connections.

mysql.go

@@ -16,6 +16,13 @@ type MySQLDriver struct {
 func normalizeMySQLURL(u *url.URL) string {
 	normalizedURL := *u
 	normalizedURL.Scheme = ""
+
+	// set default port
+	if normalizedURL.Port() == "" {
+		normalizedURL.Host = fmt.Sprintf("%s:3306", normalizedURL.Host)
+	}
+
+	// host format required by go-sql-driver/mysql
 	normalizedURL.Host = fmt.Sprintf("tcp(%s)", normalizedURL.Host)
 
 	query := normalizedURL.Query()

mysql_test.go

@@ -9,7 +9,7 @@ import (
 )
 
 func mySQLTestURL(t *testing.T) *url.URL {
-	u, err := url.Parse("mysql://root:root@mysql:3306/dbmate")
+	u, err := url.Parse("mysql://root:root@mysql/dbmate")
 	require.Nil(t, err)
 
 	return u
@@ -34,6 +34,24 @@ func prepTestMySQLDB(t *testing.T) *sql.DB {
 	return db
 }
 
+func TestNormalizeMySQLURLDefaults(t *testing.T) {
+	u, err := url.Parse("mysql://host/foo")
+	require.Nil(t, err)
+	require.Equal(t, "", u.Port())
+
+	s := normalizeMySQLURL(u)
+	require.Equal(t, "tcp(host:3306)/foo?multiStatements=true", s)
+}
+
+func TestNormalizeMySQLURLCustom(t *testing.T) {
+	u, err := url.Parse("mysql://bob:secret@host:123/foo?flag=on")
+	require.Nil(t, err)
+	require.Equal(t, "123", u.Port())
+
+	s := normalizeMySQLURL(u)
+	require.Equal(t, "bob:secret@tcp(host:123)/foo?flag=on&multiStatements=true", s)
+}
+
 func TestMySQLCreateDropDatabase(t *testing.T) {
 	drv := MySQLDriver{}
 	u := mySQLTestURL(t)