Update app.py

app.py

@@ -18,7 +18,8 @@ def main():
         st.text("Message sent!")
 
     st.text("Chat history:")
-    with open("chat.txt", "r") as f:
+    with open("chat.txt", "a+") as f:
+        f.seek(0)
         chat_history = f.read()
     st.text(chat_history)
 
@@ -31,7 +32,8 @@ def main():
         t -= 1
         if t == 0:
             countdown.text("Time's up!")
-            with open("chat.txt", "r") as f:
+            with open("chat.txt", "a+") as f:
+                f.seek(0)
                 chat_history = f.read()
             st.text(chat_history)
             t = 60