What is the role of an array inside a channel and in what scenarios is it used?

In Go, a channel is a means for data transfer between goroutines, providing synchronization and message exchange. Inside a channel, a buffer is implemented — a fixed-size array that stores elements transmitted through the channel.

The role of the array inside a channel:

• Buffering: the array acts as a buffer, allowing the sender to write several values into the channel without waiting for the receiver.
• Asynchrony: the buffer allows partial decoupling of sender and receiver, increasing performance and reducing blocking.

Scenarios for buffered channels:

• When load peaks need smoothing, allowing the sender not to block if the receiver is temporarily busy.
• For implementing message queues with limited size.

Example of creating a buffered channel of size 3:

ch := make(chan int, 3) // channel with buffer size 3

ch <- 1 // does not block, buffer not full
ch <- 2
ch <- 3

// Attempting to send a 4th element will block if no one reads
// ch <- 4

fmt.Println(<-ch) // reading from channel frees space in buffer

If the channel is unbuffered (size 0), then the array is absent, and send blocks until someone reads the value.