A channel is a communication mechanism that allows goroutines to exchange data, among other things. However, there are some definite rules here. First, each channel allows the exchange of a particular data type, which is also called the element type of the channel, and second, for a channel to operate properly, you will need someone to receive what is sent via the channel. You should declare a new channel using the chan keyword, and you can close a channel using the close() function.

Finally, a very important detail: when you are using a channel as a function parameter, you can specify its direction; that is, whether it is going to be used for sending or receiving. In my opinion, if you know the purpose of a channel in advance, you should use this capability because it will make your programs more robust as well as safer because you will not be able to send data accidentally to a channel from which you should only receive data or receive data from a channel to which you should only be sending data. As a result, if you declare that a channel function parameter will be used for reading only and you try to write to it, you will get an error message that will most likely save you from nasty bugs. We will talk about this later on in this chapter.