How to Limit the Number of Concurrent Goroutines

Use a buffered channel as a semaphore to limit the number of concurrent goroutines. Create a channel with the desired capacity, send a token before starting work, and receive a token when finished.

sem := make(chan struct{}, 10) // Limit to 10 concurrent goroutines

for _, item := range items {
    sem <- struct{}{} // Acquire token
    go func(i interface{}) {
        defer func() { <-sem }() // Release token
        process(i)
    }(item)
}

// Wait for all goroutines to finish
for range items {
    <-sem
}

Limiting the number of concurrent goroutines uses a channel with a fixed size to act like a ticket system. Only a specific number of tickets exist, so only that many workers can start at once. When a worker finishes, it returns its ticket, allowing another worker to start.