Update Open func to support keepalive

Got rid of OpenConnector for simplicity's sake.

Noticed "pq: current transaction is aborted" in go18_test.go:212,
but it doesn't seem to be related. The same issue popped up in
#921.

conn.go

@@ -48,12 +48,6 @@ func (d *Driver) Open(name string) (driver.Conn, error) {
 	return Open(name)
 }
 
-// OpenConnector parses the name in the same format that Driver.Open
-// parses the name parameter.
-func (d *Driver) OpenConnector(name string) (driver.Connector, error) {
-	return NewConnector(name)
-}
-
 func init() {
 	sql.Register("postgres", &Driver{})
 }
@@ -278,7 +272,11 @@ func (cn *conn) writeBuf(b byte) *writeBuf {
 // Most users should only use it through database/sql package from the standard
 // library.
 func Open(dsn string) (_ driver.Conn, err error) {
-	return DialOpen(defaultDialer{}, dsn)
+	c, err := NewConnector(dsn)
+	if err != nil {
+		return nil, err
+	}
+	return c.open(context.Background())
 }
 
 // DialOpen opens a new connection to the database using a dialer.

conn_test.go

@@ -14,17 +14,6 @@ import (
 	"time"
 )
 
-// testDriver is the Postgres database driver that doesn't implement DriverContext interface.
-type testDriver struct{}
-
-func (d *testDriver) Open(name string) (driver.Conn, error) {
-	return Open(name)
-}
-
-func init() {
-	sql.Register("postgres-test", &testDriver{})
-}
-
 type Fatalistic interface {
 	Fatal(args ...interface{})
 }
@@ -59,7 +48,7 @@ func testConninfo(conninfo string) string {
 }
 
 func openTestConnConninfo(conninfo string) (*sql.DB, error) {
-	return sql.Open("postgres-test", testConninfo(conninfo))
+	return sql.Open("postgres", testConninfo(conninfo))
 }
 
 func openTestConn(t Fatalistic) *sql.DB {
@@ -151,6 +140,46 @@ func TestOpenURL(t *testing.T) {
 	testURL("postgresql://")
 }
 
+func TestOpen(t *testing.T) {
+	dsn := "keepalives_interval=10"
+	c, err := Open(dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+
+	d := c.(*conn).dialer.(defaultDialer)
+	want := 10 * time.Second
+	if want != d.d.KeepAlive {
+		t.Fatalf("expected: %v, got: %v", want, d.d.KeepAlive)
+	}
+}
+
+func TestSQLOpen(t *testing.T) {
+	dsn := "keepalives_interval=10"
+	db, err := sql.Open("postgres", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	if err = db.Ping(); err != nil {
+		t.Fatal(err)
+	}
+
+	drv := db.Driver()
+	c, err := drv.Open(dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+
+	d := c.(*conn).dialer.(defaultDialer)
+	want := 10 * time.Second
+	if want != d.d.KeepAlive {
+		t.Fatalf("expected: %v, got: %v", want, d.d.KeepAlive)
+	}
+}
+
 const pgpassFile = "/tmp/pqgotest_pgpass"
 
 func TestPgpass(t *testing.T) {