go-concurrency-patterns

Create a jobs channel, spawn a fixed number of goroutines that range over it, and collect results through a results channel. Use sync.WaitGroup to wait for workers and close the results channel from a separate goroutine after wg.Wait() completes.

Use golang.org/x/sync/semaphore with a weighted limit, or a buffered channel acting as a semaphore where each goroutine acquires a slot before running. errgroup's SetLimit method also caps concurrent goroutines directly.

Use sync.Map for read-heavy workloads with infrequent writes or disjoint key sets across goroutines. For write-heavy workloads, a sharded map with per-shard RWMutex reduces lock contention better than a single mutex.

Run tests or builds with the -race flag, such as go test -race ./... or go run -race main.go. The race detector instruments memory accesses and reports conflicting unsynchronized reads and writes at runtime.

Goroutines leak when they block forever on channel sends or receives with no exit path. Prevent leaks by passing context.Context, selecting on ctx.Done(), and ensuring the sender closes channels so receivers terminate.