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Concurrency in Depth

Channel Patterns

Fan-in, fan-out, pipelines, buffered channels, and closing protocols for safe communication.

8 min readGo for SREBuild

Channel Basics

Channels are typed conduits for goroutine communication. They enforce synchronization — a send blocks until a receive is ready, and vice versa. This makes channels a powerful coordination primitive.

Gochannel-operations.go

17 linesLn 1, Col 1Go

Unbuffered channels synchronize sender and receiver. Buffered channels decouple them up to the buffer size. Close signals that no more values will be sent. The ok variable indicates whether the value came from a send or a close.

Buffered Channels

Buffered channels decouple senders and receivers. They are useful when you want to absorb bursts or when senders and receivers run at different speeds.

Gobuffered-channel-patterns.go

27 linesLn 1, Col 1Go

Buffer size controls behavior. Size 0 is synchronous. Size 1 is a signal. Size N absorbs N sends without blocking. Size len(items) collects all results without blocking senders. Choose buffer size based on the pattern.

Channel Direction

Channel direction in function signatures enforces communication patterns. Send-only and receive-only channels prevent misuse at compile time.

Godirectional-channels.go

27 linesLn 1, Col 1Go

chan<- means send-only. <-chan means receive-only. This prevents bugs: a consumer cannot accidentally send, and a producer cannot accidentally receive. The compiler enforces the communication pattern.

Closing Channels

Closing a channel signals that no more values will be sent. Receivers can detect this with the ok variable. The close protocol has strict rules: only the sender should close, and close exactly once.

Goclose-protocol-rules.go

32 linesLn 1, Col 1Go

Closing from the sender side is the only safe pattern. Multiple senders cannot safely close — they would race and panic. Receivers should use range or the ok check. Never close a channel from the receiver side unless you have complete control over all senders.

Never close a channel from the receiver side

Closing a channel from the receiver side causes panics if any sender tries to send after the close. Only the sender should close channels. If you need multiple senders, use a WaitGroup to coordinate closing.

Multiplexing with select

select waits on multiple channel operations. It is the Go equivalent of a switch statement for channels. select blocks until one case is ready, then executes it.

Goselect-patterns.go

35 linesLn 1, Col 1Go

select blocks until one case is ready. If multiple cases are ready, Go selects one randomly — this prevents starvation. default makes select non-blocking. ctx.Done() is the standard way to handle cancellation.

Common Patterns

Gochannel-patterns.go

42 linesLn 1, Col 1Go

Fan-out distributes work across workers reading from the same channel. Fan-in merges multiple channels into one. Both patterns use WaitGroup to coordinate closing the output channel. context cancellation provides the shutdown mechanism.

Mark this lesson complete to store local progress and unlock a cleaner resume path the next time you visit.

Stage 3 · Build

Concurrency in Depth

Channel Patterns

Fan-in, fan-out, pipelines, buffered channels, and closing protocols for safe communication.

8 min readGo for SREBuild

Channel Basics

Gochannel-operations.go

17 linesLn 1, Col 1Go

Buffered Channels

Buffered channels decouple senders and receivers. They are useful when you want to absorb bursts or when senders and receivers run at different speeds.

Gobuffered-channel-patterns.go

27 linesLn 1, Col 1Go

Channel Direction

Channel direction in function signatures enforces communication patterns. Send-only and receive-only channels prevent misuse at compile time.

Godirectional-channels.go

27 linesLn 1, Col 1Go

Closing Channels

Closing a channel signals that no more values will be sent. Receivers can detect this with the ok variable. The close protocol has strict rules: only the sender should close, and close exactly once.

Goclose-protocol-rules.go

32 linesLn 1, Col 1Go

Never close a channel from the receiver side

Multiplexing with select

select waits on multiple channel operations. It is the Go equivalent of a switch statement for channels. select blocks until one case is ready, then executes it.

Goselect-patterns.go

35 linesLn 1, Col 1Go

Common Patterns

Gochannel-patterns.go

42 linesLn 1, Col 1Go

Mark this lesson complete to store local progress and unlock a cleaner resume path the next time you visit.