feat(compose): async node example

[shentongmartin]

Async Lambda Node in Eino Graph

This example demonstrates an "async node" implemented as a normal lambda in an Eino graph.
It covers two realistic business scenarios:

• Report Generation (invokable): a long-running background job that produces a document URL.
• Live Transcription (streamable): a stream of tokens produced over time and converted via StreamReaderWithConvert.

Files

• service.go: mocked services (generateReport, transcribeLive).
• main.go: graph wiring, lambda nodes, and run flows.

How It Works

• The invokable lambda starts generateReport in a goroutine and blocks on a channel until completion or cancellation.
• The streamable lambda obtains a live StreamReader[string] and wraps it with StreamReaderWithConvert to transform tokens.

Run

cd compose/graph/async_node
go run .

You will see:

• A report URL logged from the invokable path.
• A stream of uppercase tokens from the transcription path until EOF.

Notes

• The services inject errors when inputs contain the word error, to showcase error propagation.
• Cancellation is respected via context.Context.