Fintech on Go: Signing, event loops, and replay protection without an SDK (Part 2)

Part 2 of a two-part case study on building an ERC-20 rewards service in Go. This one covers stdlib signing, the event loop shape that runs the async pipelines, and replay protection at the consumer end. TL;DR Signing an on-chain transaction is two library calls. crypto/ecdsa plus go-ethereum/types land it in five lines. Event pipelines are one for { select } over three channels. The same shape runs the deposit monitor and the reconciler. Reach for Zerohash, Fireblocks, or Circle first. Write th