Go's Concurrency Examples in Java 19(mccue.dev)

    synchronized (seen) {
        if (!seen.contains(u)) {
            seen.add(u);
            // ...
        }
    }

    // seen = ConcurrentHashMap.newKeySet()
    
    if (seen.add(u)) {
        // ...
    }

    package main
    
    import (
     "context"
     "fmt"
     "time"
    )
    
    func say(ctx context.Context, s string) {
     for i := 0; i < 5; i++ {
      select {
      case <-time.After(100 * time.Millisecond):
       fmt.Println(s)
      case <-ctx.Done():
       return // Operation canceled or timed out.
      }
     }
    }
    
    func main() {
     ctx := context.Background() // Use context cancellation semantics.
     go say(ctx, "world")
     say(ctx, "hello")
    }

    for i := 0; i < 5; i++ {
     func(i int) { // Wrap in closure expressly to support defer statement.
      t := time.NewTimer(100 * time.Millisecond)
      defer t.Stop()
      select {
      case <-t.C:
       fmt.Println(s)
      case <-ctx.Done():
       return // Operation canceled or timed out.
      }
     }(i)
    }