sqlx.Connect: Close db connection if db.Ping() fails

If the db open succeeds but the Ping() fails, close the
connection and return nil along with the error to prevent
resource leakage.

Fixes jmoiron#366

sqlx.go

@@ -627,10 +627,14 @@ func (r *Rows) StructScan(dest interface{}) error {
 func Connect(driverName, dataSourceName string) (*DB, error) {
 	db, err := Open(driverName, dataSourceName)
 	if err != nil {
-		return db, err
+		return nil, err
 	}
 	err = db.Ping()
-	return db, err
+	if err != nil {
+		db.Close()
+		return nil, err
+	}
+	return db, nil
 }
 
 // MustConnect connects to a database and panics on error.

sqlx_test.go

@@ -1296,10 +1296,13 @@ type Product struct {
 // tests that sqlx will not panic when the wrong driver is passed because
 // of an automatic nil dereference in sqlx.Open(), which was fixed.
 func TestDoNotPanicOnConnect(t *testing.T) {
-	_, err := Connect("bogus", "hehe")
+	db, err := Connect("bogus", "hehe")
 	if err == nil {
 		t.Errorf("Should return error when using bogus driverName")
 	}
+	if db != nil {
+		t.Errorf("Should not return the db on a connect failure")
+	}
 }
 
 func TestRebind(t *testing.T) {