added example

contracts/example/common/variables.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+contract Constants {
+    // token supported
+    address public constant token = 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48; // USDC
+}
+
+contract Variables is Constants {
+    // userAddress => amount deposited
+    mapping(address => uint256) internal _userBalance;
+}

contracts/example/module1/events.sol

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "../common/variables.sol";
+
+contract Events is Variables {
+    event supplyLog(uint256 amount_);
+
+    event withdrawLog(uint256 amount_);
+}

contracts/example/module1/main.sol

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "./events.sol";
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+
+contract UserModule is Events {
+    using SafeERC20 for IERC20;
+
+    /**
+     * @dev User function to supply.
+     * @param amount_ amount to supply.
+     */
+    function supply(uint256 amount_) external {
+        IERC20(token).safeTransferFrom(msg.sender, address(this), amount_);
+        _userBalance[msg.sender] += amount_;
+
+        emit supplyLog(amount_);
+    }
+
+    /**
+     * @dev User function to withdraw.
+     * @param amount_ amount to withdraw.
+     */
+    function withdraw(uint256 amount_) external {
+        _userBalance[msg.sender] -= amount_;
+        IERC20(token).safeTransfer(msg.sender, amount_);
+
+        event withdrawLog(uint256 amount_);
+    }
+}

contracts/example/module2/main.sol

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "../common/variables.sol";
+
+contract ReadModule is Variables {
+    /**
+     * @dev Read function to get user's balance in the contract.
+     * @param user_ address of user.
+     */
+    function userBalance(address user_) public view returns (uint256) {
+        return _userBalance[user_];
+    }
+}

package-lock.json

@@ -8,6 +8,9 @@
       "name": "infinite-proxy",
       "version": "1.0.0",
       "license": "ISC",
+      "dependencies": {
+        "@openzeppelin/contracts": "^4.5.0"
+      },
       "devDependencies": {
         "@nomiclabs/hardhat-ethers": "^2.0.5",
         "@nomiclabs/hardhat-etherscan": "^3.0.3",
@@ -1497,6 +1500,11 @@
         "hardhat": "^2.0.0"
       }
     },
+    "node_modules/@openzeppelin/contracts": {
+      "version": "4.5.0",
+      "resolved": "https://registry.npmjs.org/@openzeppelin/contracts/-/contracts-4.5.0.tgz",
+      "integrity": "sha512-fdkzKPYMjrRiPK6K4y64e6GzULR7R7RwxSigHS8DDp7aWDeoReqsQI+cxHV1UuhAqX69L1lAaWDxenfP+xiqzA=="
+    },
     "node_modules/@resolver-engine/core": {
       "version": "0.3.3",
       "resolved": "https://registry.npmjs.org/@resolver-engine/core/-/core-0.3.3.tgz",
@@ -24098,6 +24106,11 @@
         "@types/web3": "1.0.19"
       }
     },
+    "@openzeppelin/contracts": {
+      "version": "4.5.0",
+      "resolved": "https://registry.npmjs.org/@openzeppelin/contracts/-/contracts-4.5.0.tgz",
+      "integrity": "sha512-fdkzKPYMjrRiPK6K4y64e6GzULR7R7RwxSigHS8DDp7aWDeoReqsQI+cxHV1UuhAqX69L1lAaWDxenfP+xiqzA=="
+    },
     "@resolver-engine/core": {
       "version": "0.3.3",
       "resolved": "https://registry.npmjs.org/@resolver-engine/core/-/core-0.3.3.tgz",

package.json

@@ -47,5 +47,8 @@
     "ts-node": "^10.7.0",
     "typechain": "^5.2.0",
     "typescript": "^4.6.3"
+  },
+  "dependencies": {
+    "@openzeppelin/contracts": "^4.5.0"
   }
 }