I want two thread two functions as I stated. Specifically

public static void playerInput()
{
    while (true)
    {
    ConsoleKeyInfo pressedKey = Console.ReadKey();
    Doors.input = pressedKey.KeyChar;
    Console.Write('b');
    }
}

And

public static void openingDoor()

{

    while (true)

    {

        if (Doors.input == 'o')

        {

            openDoor();

            Console.WriteLine($"You're now at door {door}");

            input = ' ';

        }

    }

}

opendoor() is a function that just increments a value by 1.

I tried doing

Thread pInput = new Thread(playerInput);

Thread doorOpen = new Thread(openingDoor);

pInput.Start();
doorOpen.Start();

pInput.Join();

doorOpen.Join();

At first it seemed working fine, but after pressing o for like 6 times, it crashes my compiler and gives this error:

System.NullReferenceException: Object reference not set to an instance of an object

at System.Timers.Timer.UpdateTimer()

at System.Timers.Timer.set_Enabled(Boolean value)

at CSharpShellCore.IDE.Views.ConsoleView.QueueWriteLine(String text)

at System.Object.CallSite.Target(Closure , CallSite , Object , String )

at CSharpShellCore.Console.WriteLineToView(Object o)

at CSharpShellCore.Console.WriteLine(String n)

at Doors.Doors.openingDoor()

at System.Threading.Thread.StartCallback()

*** **** ***System.NullReferenceException: Object reference not set to an instance of an object

at System.Timers.Timer.UpdateTimer() 

at System.Timers.Timer.set_Enabled(Boolean value) 

at CSharpShellCore.IDE.Views.ConsoleView.QueueWriteLine(String text) 

at System.Object.CallSite.Target(Closure, CallSite, Object, String) 

at CSharpShellCore.Console.WriteLineToView(Object o) 

at CSharpShellCore.Console.WriteLine(String n) 

at Doors.Doors.openingDoor() 

at System.Threading.Thread.StartCallback()