Getting an asset price from EVM chain

Table of Contents

• About The Project
• Prerequisites
• Installation
• Usage

About The Project

The project shows how to retrieve asset price from any EVM chain. The price data feed contract addresses can be found here.

📘 Note on Go bindings aggregator_v3_interface.go

Follow these steps to learn how to generate this file:

1. Generate the Contract ABI from a solidity source file using solc. In this case, we are going to download the AggregatorV3Interface and generate an ABI called AggregatorV3Interface.abi:

wget https://raw.githubusercontent.com/smartcontractkit/chainlink/develop/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol
solc --abi AggregatorV3Interface.sol -o .

2. From AggregatorV3Interface.abi, generate the Go bindings aggregator_v3_interface.go required to programmatically interact with a smart contract > using generated, typesafe Gocode. Ensure that Geth is installed so you can use > > > abigen.

abigen --abi=AggregatorV3Interface.abi --pkg=aggregator_v3_interface --out=aggregator_v3_interface.go

Prerequisites

• Go
• Be familiar with Chainlink Data Feeds and Chainlink Data Feeds Contract Addresses.

Installation

1. Get a RPC API Key from a node provider such as Alchemy, Infura, Moralis, or QuickNode. This example uses the Rinkeby testnet.
2. Clone the repo

   git clone https://github.com/smartcontractkit/smart-contract-examples.git

3. Enter the direcory

   cd pricefeed-golang

4. Copy the example environment file .env.example to create .env file

   cp .env.example .env

5. In .env file , replace REPLACE_BY_YOUR_RPC_URL by the RPC_URL of the EVM chain you want to connect to.
6. In .env file , replace REPLACE_BY_PRICE_FEED_PROXY_ADDR by the price feed address. For instance, 0x8A753747A1Fa494EC906cE90E9f37563A8AF630e if you want the ETH/USD price feed on the Rinkeby testnet.

Usage

After the installation step, run the example

go run main.go

2022/05/18 18:48:26 ETH / USD Price feed address is 0x8A753747A1Fa494EC906cE90E9f37563A8AF630e
2022/05/18 18:48:26 Round id is 36893488147419115714
2022/05/18 18:48:26 Answer is 195086228530
2022/05/18 18:48:26 Formatted answer is 1950.8622853
2022/05/18 18:48:26 Started at 2022-05-18 18:10:36 +0200 CEST
2022/05/18 18:48:26 Updated at 2022-05-18 18:10:36 +0200 CEST
2022/05/18 18:48:26 Answered in round 36893488147419115714

Note that you can also override the price feed address on the command line. For instance:

go run main.go 0x78F9e60608bF48a1155b4B2A5e31F32318a1d85F

2022/05/18 18:48:46 EUR / USD Price feed address is 0x78F9e60608bF48a1155b4B2A5e31F32318a1d85F
2022/05/18 18:48:46 Round id is 73786976294838233703
2022/05/18 18:48:46 Answer is 104976000
2022/05/18 18:48:46 Formatted answer is 1.04976
2022/05/18 18:48:46 Started at 2022-05-18 18:45:36 +0200 CEST
2022/05/18 18:48:46 Updated at 2022-05-18 18:45:36 +0200 CEST
2022/05/18 18:48:46 Answered in round 73786976294838233703