Microsoft Visual Studio Code doesn't do anything when running an executable - c++

Question

I wanted to create a simple local web server using this library.
So, I created a new project in Visual Studio, created main.cpp and type in this code into my main.cpp.
#include "httplib.h"
using namespace httplib;
int main(void) {
Server svr;
svr.Get("/hi", [](const Request & /*req*/, Response &res) {
res.set_content("Hello World!", "text/plain");
});
svr.listen("localhost", 8080);
}
And I also created httplib.h and copied this code into my httplib.h.
I ran it. A blank terminal pop-up, then I go to localhost:8080/hi via Google Chrome and it works. There's "Hello World" output in there.
Then, I do the same thing with Visual Studio Code. But when I compile it, there's an error says
/usr/bin/ld: /tmp/ccUgoSsW.o: in function
'std::thread::thread<httplib::ThreadPool::worker, ,
void>(httplib::ThreadPool::worker&&)':
/usr/include/c++/9/thread:126:
undefined reference to `pthread_create'
collect2: error: ld returned 1 exit status
I searched a bit and found a solution. So, I compile it manually using Visual Studio Code terminal by typing "g++ main.cpp -o demo -pthread" and it compiled successfully. But, then I try to run the demo via terminal "./demo" it just doesn't do anything. I try to connect to localhost:8080/hi via Google Chrome but it said This site can’t be reached.
How to reproduce my problem
1- Create a folder
2- Create a main.cpp in that folder and type in this code into it
#include "httplib.h"
using namespace httplib;
int main(void) {
Server svr;
svr.Get("/hi", [](const Request & /*req*/, Response &res) {
res.set_content("Hello World!", "text/plain");
});
svr.listen("localhost", 8080);
}
3- Create a httplib.h file into the folder and copy this code into it
4- Compile it via Visual Studio Code terminal by using this command "g++ main.cpp -o demo -pthread"
5- Run the build via terminal by using this command "./demo"
6- Go to Google Chrome and type this address "localhost:8080/hi" If it can't be accessed then that's my problem
ps: I'm using WSL2 Ubuntu 20.04