91 lines
1.9 KiB
Go
91 lines
1.9 KiB
Go
package main
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import (
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"context"
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"errors"
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"fmt"
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"time"
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)
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// ============================================================================
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// 💡 GO 11: MUSTERLÖSUNG (select, Timeouts & Context)
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// ============================================================================
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var ErrTimeout = errors.New("timeout exceeded")
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// FastestResponse liest mit select den Kanal aus, der zuerst liefert.
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func FastestResponse(ch1, ch2 <-chan string) string {
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select {
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case res := <-ch1:
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return res
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case res := <-ch2:
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return res
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}
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}
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// FetchWithTimeout liest aus dem Kanal oder bricht nach Ablauf der Zeit ab.
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func FetchWithTimeout(ch <-chan string, timeout time.Duration) (string, error) {
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select {
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case res := <-ch:
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return res, nil
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case <-time.After(timeout):
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return "", ErrTimeout
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}
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}
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// TrySend sendet nicht-blockierend in den Kanal.
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func TrySend(ch chan<- int, val int) bool {
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select {
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case ch <- val:
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return true
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default:
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return false
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}
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}
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// TryReceive liest nicht-blockierend aus dem Kanal.
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func TryReceive(ch <-chan int) (int, bool) {
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select {
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case val := <-ch:
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return val, true
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default:
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return 0, false
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}
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}
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// QueryWithContext führt eine Funktion asynchron aus und reagiert auf context.Done().
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func QueryWithContext(ctx context.Context, fn func() string) (string, error) {
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resCh := make(chan string, 1)
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go func() {
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resCh <- fn()
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}()
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select {
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case <-ctx.Done():
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return "", ctx.Err()
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case res := <-resCh:
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return res, nil
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}
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}
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func main() {
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fmt.Println("=== Go 11: Musterlösung ===")
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fastCh := make(chan string, 1)
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slowCh := make(chan string, 1)
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fastCh <- "Antwort von Node-A (10ms)"
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slowCh <- "Antwort von Node-B (150ms)"
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winner := FastestResponse(fastCh, slowCh)
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fmt.Println("Schnellster Server:", winner)
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unresponsiveCh := make(chan string)
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res, err := FetchWithTimeout(unresponsiveCh, 50*time.Millisecond)
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if err != nil {
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fmt.Printf("Erwarteter Timeout-Fehler: %v\n", err)
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} else {
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fmt.Println("Ergebnis:", res)
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}
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}
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