Verilog queue module with 4 places

I am trying to make a module that will work like a queue with 4 slots. It is for an elevator and the currSt is the current state and destination is the first item in queue. 4'b1111 is like NULL. The problem here is that the queue doesn't get the input from the keyboard to be stored in the 4 free places. `

module Queue(
  input clk, slowclk,
  input[3:0] cs,
  output[3:0] currstat, des,
  input[3:0]keycode,
  output reg go
);

reg currSt;
initial currSt = 4'b1;
//1111 = empty place in queue
reg queueItem1 = 4'b1111;
reg queueItem2 = 4'b1111;
reg queueItem3 = 4'b1111;
reg queueItem4 = 4'b1111;

//continuous assignment
assign currstat = currSt;
assign des = (queueItem1 == 4'b1111)?currSt:queueItem1;

always@(posedge clk) begin
    if ((keycode == 4'b0001)
      ||(keycode == 4'b0010)
      ||(keycode == 4'b0100)
      ||(keycode == 4'b1000))
    begin
        if(queueItem1 == 4'b1111)
            queueItem1 = keycode;
        else if(queueItem2 == 4'b1111)
            queueItem2 = keycode;
        else if(queueItem3 == 4'b1111)
            queueItem3 = keycode;
        else if(queueItem4 == 4'b1111)
            queueItem4 = keycode;
        //else do nothing
    end

    //adds new key pressed to queue
    if (keycode == 4'b0001
     || keycode == 4'b0010
     || keycode == 4'b0100
     || keycode == 4'b1000)
    begin
        if (queueItem1 != keycode
         && queueItem2 != keycode
         && queueItem3 != keycode
         && queueItem4 != keycode)
        begin
            if (queueItem1 == 4'b1111
             && queueItem2 == 4'b1111
             && queueItem3 == 4'b1111
             && queueItem4 == 4'b1111)
              queueItem1 = keycode;
            else if (queueItem1 != 4'b1111
                  && queueItem2 == 4'b1111
                  && queueItem3 == 4'b1111
                  && queueItem4 == 4'b1111)
              queueItem2 = keycode;
            else if (queueItem1 != 4'b1111
                  && queueItem2 != 4'b1111
                  && queueItem3 == 4'b1111
                  && queueItem4 == 4'b1111)
              queueItem3 = keycode;
            else if (queueItem1 != 4'b1111
                  && queueItem2 != 4'b1111
                  && queueItem3 != 4'b1111
                  && queueItem4 == 4'b1111)
                queueItem4 = keycode;
            //else don't add the new one in the queue
        end
        //else if any of the slots is equal the keycode then dont add it
    end

    //check if current state matches with the request queue
    if (currSt == 4'b1000
     || currSt == 4'b0100
     || currSt == 4'b0010
     || currSt == 4'b0001)
    begin
        if (queueItem1 == currSt) begin
            queueItem1 = queueItem2;
            queueItem2 = queueItem3;
            queueItem3 = queueItem4;
            queueItem4 = 4'b1111;
            go = 0;
        end else if (queueItem2 == currSt) begin
            queueItem2 = queueItem3;
            queueItem3 = queueItem4;
            queueItem4 = 4'b1111;
            go = 0;
        end else if (queueItem3 == currSt) begin
            queueItem3 = queueItem4;
            queueItem4 = 4'b1111;
            go = 0;
        end else if (queueItem4 == currSt) begin
            queueItem4 = 4'b1111;
            go = 0;
        end

        //if current state is not in the request queue
        else 
            go = 1;
    end
end

always@(posedge slowclk)//change current state to new state
    currSt <= cs;

endmodule