Blog / Go Language Spec

Channel types

May 16, 2023

Channel types

A channel provides a mechanism for concurrently executing functions to communicate by sending and receiving values of a specified element type. The value of an uninitialized channel is nil.

ChannelType = ( "chan" | "chan" "<-" | "<-" "chan" ) ElementType .

Channels are one of the most confusing parts of Go, for many newcomers. But they don’t need to be. They’re actually quite simple.

Think of a channel as an array, which can only be read from one end, and appended to the other.

There are a few other rules around how channels work, which we’ll of course get to, but from a data type standpoint, that serves as a useful summary.

There are no magical scoping or garbage collection rules. Channels don’t do anything. They’re just a data type. They just hold data, and they go out of scope, get garbage collected, can be passed around, assigned, re-assigned, just as any other type can.

Quotes from The Go Programming Language Specification Version of December 15, 2022

Share this

Direct to your inbox, daily. I respect your privacy .

Unsure? Browse the archive .

Related Content

Directional channels

Channel types … The optional <- operator specifies the channel direction, send or receive. If a direction is given, the channel is directional, otherwise it is bidirectional. A channel may be constrained only to send or only to receive by assignment or explicit conversion. chan T // can be used to send and receive values of type T chan<- float64 // can only be used to send float64s <-chan int // can only be used to receive ints When you create a new channel, you get a bidirectional channel.

The Done channel

May I rant for a moment? I don’t like the way GoDoc works for structs and interfaces. And below is a demonstration as to why. It’s not possible to link directly to an interface method or struct field, and the formatting is ugly. sigh type Context type Context interface { … // Done returns a channel that's closed when work done on behalf of this // context should be canceled. Done may return nil if this context can // never be canceled.

Close

Today we’re looking at the close built-in function. There’s not really any new information here, as we’ve already talked about channels, but it’s a good opportunity to review. Close For an argument ch with a core type that is a channel, the built-in function close records that no more values will be sent on the channel. It is an error if ch is a receive-only channel. Sending to or closing a closed channel causes a run-time panic.

Get daily content like this in your inbox!

Subscribe