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Packages, Modules & Concurrency Intro

Channels

Communicate safely between goroutines using channels — Go's built-in typed message pipes.

8 min readProgramming Foundations (Go)Code

Creating and Using Channels

A channel is a typed conduit for sending values between goroutines. Send with ch <- value and receive with value := <-ch. By default, both operations block until the other side is ready.

Gobasic-channel-communication.go

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Each goroutine sends one value to `ch`. Main receives two values — both receives block until their corresponding send arrives. The total is their sum.

Do not communicate by sharing memory; share memory by communicating

This is Go's concurrency mantra. Instead of having goroutines write to shared variables (which requires mutexes), pass data through channels. The ownership of a value transfers when it is sent — the sender no longer touches it.

Buffered Channels

A buffered channel has a capacity. Sends block only when the buffer is full; receives block only when the buffer is empty. Use buffering to decouple producers and consumers.

Gobuffered-channels-as-queues.go

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The semaphore pattern uses a buffered channel to limit the number of concurrent goroutines. Sending into the semaphore acquires a slot; receiving releases it. This is safer and simpler than managing a goroutine pool manually.

Closing and Ranging

close(ch) signals that no more values will be sent. Receivers can detect closure via the comma-ok form or by ranging — range ch loops until the channel is closed and drained.

Goproducer-closes,-consumer-ranges.go

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`generate` is a common Go pattern: a function that returns a read-only channel and starts a goroutine that feeds it. The goroutine closes the channel when done. Callers range over the result naturally.

select

select waits on multiple channel operations simultaneously, picking whichever is ready first. If multiple are ready, it chooses one at random.

Goselect-with-timeout.go

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`time.After` returns a channel that receives after a duration — the canonical timeout idiom. A `default` case makes `select` non-blocking: it runs immediately if no other case is ready.

Channel Directions

Function parameters can declare a channel as send-only (chan<-) or receive-only (<-chan). This documents intent and prevents accidental misuse at compile time.

Godirectional-channels-in-function-signatures.go

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A bidirectional `chan int` is automatically convertible to `chan<- int` or `<-chan int` when passed to a function. The directional types are only restrictions — they never require explicit conversion.

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