Blockchain Price Oracle

Real-time cryptocurrency price oracle

What it does

1. Fetches BTC/ETH prices from CoinGecko every minute
2. Updates smart contract when price differs >2% from on-chain AND <20% from Chainlink
3. Streams contract price changes (all sources) via WebSocket
4. Serves current prices, time-range history, history of reverts
5. Zero reverts - prevents gas waste by pre-TX validation and by waiting previously sent TX for chosen symbol to be completed
6. Multi-instance ready - easy to add distributed lock coordination to keep contract reverts at zero when multiple instances are running at the same time
7. Extensible - easy to add new symbols (BTC/ETH/SOL/...) when contract supports it

Setup

Create .env file in root directory

ENV

ANKR_SEPOLIA_API_KEY=your_ankr_key
WSS_URL=wss://eth-sepolia.g.alchemy.com/v2/your_key
CONTRACT_ADDR=0xFf0fCE651EB5C7C147Af111f89dCB25AB57407e8
PRIVATE_KEY=0xabcdef...  # 64 hex chars (no 0x prefix)

Run

go mod tidy
go run app/main.go

Provided API Endpoints

Endpoint	Method	Description
/api/v1/prices/:symbol	GET	Current prices (on-chain+CL+CG)
/api/v1/prices/:symbol/last	GET	Last N prices (?n=10)
/api/v1/prices/:symbol/range	POST	Time range query for prices
/api/v1/reverts	GET	Revert history (?n=100)
/api/v1/health	GET	Server status

Tech Stack

• Go 1.25.0
• Gin
• Ethereum Sepolia
• Solidity ^0.8.20
• go-ethereum
• Alchemy WSS
• Ankr Sepolia
• CoinGecko API
• Chainlink Price Feeds
• Storage: In-memory FIFO