const login = async (payload) => {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      if (payload){
        if (payload.username === 'admin' && payload.password == 'admin'){
          resolve({status:"ok",message:"",token:"123"});
        }
        else {
          reject(new Error("Invalid Username or Password"));
        }
      }
      else {
        reject(new Error("Server side error"));
      }       
    }, 2000);
  });
};

// Example Usage - just like regular HTTP Call, this will simulate certain delay
try {
    const res = await login({username:"admin",password:"admin"});
    console.log('success!',res.token);
}
catch(err){
    console.log('error!',err.message);
}

// Example 2 - Promise All

await Promise.all([login({username:"admin",password:"admin"}), 
                   login({username:"admin",password:"admin"}), 
                   login({username:"admin",password:"admin"})]);
// array results

await Promise.all([login({username:"admin",password:"admin"}), 
                   login({username:"admin",password:"x"}), 
                   login()]);
// VM963:10 Uncaught Error: Invalid Username or Password