driver: address review comments

Author: lance6716

driver/driver.go

@@ -113,7 +113,7 @@ func parseDSN(dsn string) (connInfo, error) {
 	if parseErr != nil {
 		// If parsing fails, try to rewrite `tcp(127.0.0.1:3306)` to `127.0.0.1:3306` and try again.
 		// This is for compatibility with go-sql-driver/mysql.
-		dsn = compatDSNre.ReplaceAllString(dsn, "${1}${2}")
+		dsn = compatDSNre.ReplaceAllString(dsn, "$1$2")
 		parsedDSN, parseErr = url.Parse(dsn)
 		if parseErr != nil {
 			return ci, errors.Errorf("invalid dsn, must be user:password@addr[/db[?param=X]]")

driver/driver_test.go

@@ -102,6 +102,7 @@ func TestParseDSN(t *testing.T) {
 		"user:password@127.0.0.1/db":                    {standardDSN: true, addr: "127.0.0.1", user: "user", password: "password", db: "db", params: url.Values{}},
 		"user:password@127.0.0.1:3308/db":               {standardDSN: true, addr: "127.0.0.1:3308", user: "user", password: "password", db: "db", params: url.Values{}},
 		"user:password@tcp(127.0.0.1:3309)/db":          {standardDSN: true, addr: "127.0.0.1:3309", user: "user", password: "password", db: "db", params: url.Values{}},
+		"tcp(127.0.0.1:3310)/db":                        {standardDSN: true, addr: "127.0.0.1:3310", user: "", password: "", db: "db", params: url.Values{}},
 		"user:password@tcp(127.0.0.1:3309)/db?param=func(1)": {
 			standardDSN: true,
 			addr:        "127.0.0.1:3309",