Goroutines, I presume

January 3, 2019

It’s in Chapter 1 of Donovan and Ritchie’s “The Go Programming Language” (2016) that we first encounter the famous goroutine.

We learn that everything we’ve done leading up to this point has been running within a goroutine - the default, main one. Suddenly we see we can create more using the go keyword. That’s cool, but on their own, goroutines can never be super-useful. When we connect them together however; then all kinds of madness could ensue.

We do this connecting via channels which we create using the keyword make.Not to be confused with the UNIX make command. Channels allow us to pass values (NOTE: not references) of a specified type to other goroutines.

To me, the syntax seemed a little hairy at first sight, and that’s what I’m going to pick at a tiny bit in this post.

We’re told that:

when one goroutine attempts to send or receive on a channel, it blocks until another goroutine attempts the corresponding receive or send operation, at which point the value is transferred and both goroutines proceed. Donovan and Ritchie, The Go Programming Language, (2016) pp.18

In order to achive this we have to “make” our channel

ch := make(chan string)

We also have to create new goroutines

go fetch(url, ch) // start a goroutine

And from each of these new goroutines send a value on channel ch

ch <- fmt.Sprint(err) // send to channel ch

Which are received (and printed) by channel main

fmt.Println(<-ch) // receive from channel ch

So why do I say “hairy”? I’ll admit, I used to hate symbols like “<-” and “<=“Back in my Scala days. but I got over that. What seems a little arbitrary hereperhaps I’m just being hyper-sensitive knowing that gofmt is watching my every move.” is the space before the arrow in constructs like ch <- but the lack of one after it, for example, in <-ch. It feels to me like they should both be either one thing or the other format-wise.

However, I’ve been on the programming block long enough to know that differences like this are rarely accidental. Rather, they typically point to something far more fundamental which I’m just not aware of yet. I’m going to keep my eye on things as I read on, and follow up this post if / when I discover anything pertinent.