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Async & Concurrency Reference

Kyna integrates asynchronous operations directly into the language through async function definitions and the await prefix expression.

Asynchronous Functions: async fn​

Functions that perform non-blocking operations such as networking, disk I/O, or timers are declared with async fn:

async fn fetchUserProfile(userId: int): str {
    const url = "https://api.kyna.dev/users/" + userId;
    const raw = await fetch(url, { timeout: 5000 });
    return raw;
}

Awaiting Values: await​

The await keyword pauses evaluation of the current asynchronous execution flow until the target operation resolves, without blocking other concurrent tasks on the runtime event loop:

async fn main() {
    print("Initiating requests...");

    const userPromise = await fetchUserProfile(42);
    print("Profile received:", userPromise);
}

await main();

Error Handling in Async Contexts​

Async operations use standard try / catch blocks to capture timeouts, DNS resolution failures, and rejected network requests:

async fn safeFetch(url: str): str? {
    try {
        const response = await fetch(url, { timeout: 3000 });
        return response;
    } catch (err) {
        print("Async fetch failed with code:", err.code);
        print("Message:", err.message);
        return null;
    }
}

Concurrency Patterns & Best Practices​

  1. Explicit Timeouts: Always specify a timeout option (in milliseconds) when calling fetch() to prevent infinite hangs.
  2. Graceful Degradation: Pair nullable returns (T?) with try / catch around network borders to handle offline conditions safely.
  3. Structured Logging: Log request duration by capturing time.nowMs() before and after await calls.