GOLANG

Anatomy of Channels in Go - Concurrency in Go

Uday Hiwarale
RunGo

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What are the channels?

A channel is a communication object using which goroutines can communicate with each other. Technically, a channel is a data transfer pipe where data can be passed into or read from. Hence one goroutine can send data into a channel, while other goroutines can read that data from the same channel.

Declaring a channel

Go provides chan keyword to create a channel. A channel can transport data of only one data type. No other data types are allowed to be transported from that channel.

https://play.golang.org/p/iWOFLfcgfF-

Above program declares a channel c which can transport data type of int. Above program prints <nil> because zero-value of a channel is nil. But a nil channel is not useful. You can not pass data to or read data from a channel which is nil. Hence, we have to use make function to create a ready-to-use channel.

https://play.golang.org/p/N4dU7Ql9bK7

We have used short-hand syntax := to make a channel using make function. The above program yields the following result.

type of `c` is chan int
value of `c` is 0xc0420160c0

Notice value of the channel c. Looks like it is a memory address. Channels by default are pointers. Mostly, when you want to communicate with a goroutine, you pass the channel as an argument to the function or method. Hence when goroutine receives that channel as an argument, you don’t need to dereference it to push or pull data from that channel.

Data read and write

Go provide very easy to remember left arrow syntax <- to read and write data from a channel.

c <- data

Above syntax means, we want to push or write data to the channel c. Look at the direction of the arrow. It points from data to channel c. Hence we can imagine that we are trying to push data to c.

<- c

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