use default port if port is missing in dsn (go-sql-driver#668) (go-sql-driver#669)

Author: bgaifullin

README.md

@@ -101,7 +101,8 @@ See [net.Dial](https://golang.org/pkg/net/#Dial) for more information which netw
 In general you should use an Unix domain socket if available and TCP otherwise for best performance.
 
 #### Address
-For TCP and UDP networks, addresses have the form `host:port`.
+For TCP and UDP networks, addresses have the form `host[:port]`.
+If `port` is omitted, the default port will be used.
 If `host` is a literal IPv6 address, it must be enclosed in square brackets.
 The functions [net.JoinHostPort](https://golang.org/pkg/net/#JoinHostPort) and [net.SplitHostPort](https://golang.org/pkg/net/#SplitHostPort) manipulate addresses in this form.
 

dsn.go

@@ -376,6 +376,9 @@ func ParseDSN(dsn string) (cfg *Config, err error) {
 		}
 
 	}
+	if cfg.Net == "tcp" {
+		cfg.Addr = ensureHavePort(cfg.Addr)
+	}
 
 	return
 }
@@ -575,3 +578,10 @@ func parseDSNParams(cfg *Config, params string) (err error) {
 
 	return
 }
+
+func ensureHavePort(addr string) string {
+	if _, _, err := net.SplitHostPort(addr); err != nil {
+		return net.JoinHostPort(addr, "3306")
+	}
+	return addr
+}

dsn_test.go

@@ -65,7 +65,14 @@ var testDSNs = []struct {
 }, {
 	"unix/?arg=%2Fsome%2Fpath.ext",
 	&Config{Net: "unix", Addr: "/tmp/mysql.sock", Params: map[string]string{"arg": "/some/path.ext"}, Collation: "utf8_general_ci", Loc: time.UTC, AllowNativePasswords: true},
-}}
+}, {
+	"tcp(127.0.0.1)/dbname",
+	&Config{Net: "tcp", Addr: "127.0.0.1:3306", DBName: "dbname", Collation: "utf8_general_ci", Loc: time.UTC, AllowNativePasswords: true},
+}, {
+	"tcp(de:ad:be:ef::ca:fe)/dbname",
+	&Config{Net: "tcp", Addr: "[de:ad:be:ef::ca:fe]:3306", DBName: "dbname", Collation: "utf8_general_ci", Loc: time.UTC, AllowNativePasswords: true},
+},
+}
 
 func TestDSNParser(t *testing.T) {
 	for i, tst := range testDSNs {