Concurrency

Sun, 04 Oct 2026 00:00:00 +0000

Don’t communicate by sharing memory; share memory by communicating.

Building blocks

Tool	What it is
`go f()`	Starts a goroutine: a function running concurrently, with a few KB of stack. Thousands are cheap.
`chan T`	Typed pipe between goroutines. Unbuffered = handoff, buffered = queue.
`select`	Wait on several channel operations at once; `default` makes it non-blocking.
`context.Context`	Carries cancellation, deadlines and request-scoped values down the call tree.
`sync.Mutex` / `RWMutex`	Plain locks, for when shared state is simpler than channels.
`sync.WaitGroup`	Wait for a group of goroutines to finish.
`sync.Once` / `OnceValue`	Lazy one-time initialisation.
`errgroup` (`golang.org/x/sync`)	WaitGroup + first error + cancel the rest.

ch := make(chan int)
go func() { ch <- compute(1) }()
result := <-ch

One channel per subscriber, and a non-blocking send so a slow client can never stall the publisher.