proxy is not setting up in react

I have setup proxy in react package.json but the request is being sent to client-server instead of backed API I am using axios to consume API

my package.json

{
  "name": "front",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@material-ui/core": "^4.11.3",
    "@material-ui/icons": "^4.11.2",
    "@testing-library/jest-dom": "^5.16.4",
    "@testing-library/react": "^13.3.0",
    "@testing-library/user-event": "^13.5.0",
    "axios": "^0.27.2",
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "react-router-dom": "^5.2.0",
    "react-scripts": "5.0.1",
    "web-vitals": "^2.1.4"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "proxy": "http://localhost:8000/api"
}

sample request

 useEffect(() => {
    const fetchPost = async () => {
      const response = await axios.get(
        "posts/timeline"
      );
    };
    fetchPost();
  }, []);

the request URL in the network tab is http://localhost:3000/posts/timeline

if anyone has fixes please suggest them.