The TypeScript type definitions for the subscribe callback were too restrictive, only allowing synchronous callbacks that return void. This caused SonarLint to throw warnings when using async callbacks as shown in the README example:

const consumer = await q.subscribe({noAck: true}, async (msg) => {
  console.log(msg.bodyToString())
  await consumer.cancel()
})

The warning was:

Promise returned in function argument where a void return was expected.sonarlint(typescript:S6544)

However, the runtime already supports async callbacks - this was confirmed by existing tests that use async callbacks successfully. The issue was purely in the TypeScript type definitions being overly restrictive.

This PR updates the callback type signature from (msg: AMQPMessage) => void to (msg: AMQPMessage) => void | Promise<void> in:

• src/amqp-queue.ts - subscribe method
• src/amqp-channel.ts - basicConsume method
• src/amqp-consumer.ts - constructor and onMessage property

The change is minimal and surgical, only updating type signatures to match the actual runtime behavior. No functional code changes were required. This maintains full backward compatibility with existing synchronous callbacks while properly supporting asynchronous ones.

After this change, the README example and any other code using async callbacks in subscribe methods will compile without TypeScript/SonarLint warnings.

Fixes #92.

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