docs: connect go

docs/examples/go/connectexample/main.go

@@ -12,12 +12,13 @@ func main() {
 	dsn := os.Getenv("TDENGINE_GO_DSN")
 	taos, err := sql.Open("taosRestful", dsn)
 	if err != nil {
-        fmt.Println("failed to connect TDengine, err:", err)
+		fmt.Println(err)
 		return
 	}
-    _, err = taos.Exec("select server_version()")
+	_, err = taos.Query("select server_version()")
 	if err != nil {
 		fmt.Println(err)
+		return
 	}
 	fmt.Println("connect success")
 	defer taos.Close()