try

main.py

@@ -1,7 +1,21 @@
-from fastapi import FastAPI
+import streamlit as st
+import google.generativeai as genai
+import os
 
-app = FastAPI()
+def main():
+    GOOGLE_API_KEY = os.environ.get('GOOGLE_API_KEY')
+    genai.configure(api_key=GOOGLE_API_KEY)
+    model = genai.GenerativeModel('gemini-1.5-flash')
+    
+    if prompt := st.chat_input("哈囉！請問有什麼是我可以幫忙的嗎？"):
+        with st.chat_message("user"):
+            st.markdown(prompt)
 
-@app.get("/")
-def greet_json():
-    return {"Hello": "World!"}
+        with st.chat_message("assistant"):
+            def reply():
+                for chunk in model.generate_content(contents=prompt, stream=True):
+                    yield chunk.text
+            st.write_stream(reply)
+
+if __name__=="__main__":
+    main()