add abigen uniswapv2 example (#798)

examples/uniswapv2.rs

@@ -0,0 +1,32 @@
+use anyhow::Result;
+use ethers::prelude::*;
+use std::sync::Arc;
+
+// Generate the type-safe contract bindings by providing the ABI
+// definition in human readable format
+abigen!(
+    IUniswapV2Pair,
+    r#"[
+        function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast)
+    ]"#,
+);
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let client = Provider::<Http>::try_from(
+        "https://mainnet.infura.io/v3/c60b0bb42f8a4c6481ecd229eddaca27",
+    )?;
+    let client = Arc::new(client);
+
+    // ETH/USDT pair on Uniswap V2
+    let address = "0x0d4a11d5EEaaC28EC3F61d100daF4d40471f1852".parse::<Address>()?;
+    let pair = IUniswapV2Pair::new(address, Arc::clone(&client));
+
+    // getReserves -> get_reserves
+    let (reserve0, reserve1, _timestamp) = pair.get_reserves().call().await?;
+    println!("Reserves (ETH, USDT): ({}, {})", reserve0, reserve1);
+
+    let mid_price = f64::powi(10.0, 18 - 6) * reserve1 as f64 / reserve0 as f64;
+    println!("ETH/USDT price: {:.2}", mid_price);
+    Ok(())
+}