C++11 extension Error in VSCode and MacOS

I try to run my project in vscode but got "warning: 'auto' type specifier is a C++11 extension [-Wc++11-extensions]". I did change the C++ extension in VSCode to c++11, my tasks.json is also states "-std=c++17", but still got that warning. Any ideas? I have browsed Stackoverflow for two days to fix it but still hopeless.