How to Use semaphore.Weighted for Concurrency Limiting

Use golang.org/x/sync/semaphore to create a weighted semaphore that limits concurrent operations by acquiring tokens with specific weights.

import "golang.org/x/sync/semaphore"

// Create a semaphore allowing 5 concurrent units of work
sem := semaphore.NewWeighted(5)

// Acquire 2 units of work (blocks if insufficient capacity)
if err := sem.Acquire(ctx, 2); err != nil {
    return err
}
defer sem.Release(2)

// Perform your work here

Think of a weighted semaphore as a ticket system where different tasks need different numbers of tickets to run. You set a total limit on available tickets, and each task grabs the specific amount it needs before starting. This prevents too many heavy tasks from running at once while allowing smaller tasks to fit in the gaps.