Go from a Ruby perspective

update I wrote a follow up post.

I’m notably lacking is any C/C++ skills aside from the basic course at the university. This is why I took up Go. Google App Engine is of interest to me because I have prior experience with Heroku and AWS and no desire to maintain a server capable of running Go. The pet project I use to explore Go and GAE is on Github and called Flipco.in.

There are things I like about Go and GAE and things I don’t. Below I’ll explain what I think is wrong with Go on GAE. TL;DR it’s not ready for anything but serious experimentation.

Passing of the context

Whenever doing anything related to a GAE feature like storage a appengine.Context is required. I understand why this is necessary. And I found out that the Go community has strong feelings about ‘magic’ (it doesn’t like it). But passing along the context var in every function call hardly seems optimal. This issue might boil down to my inexperience as a Go programmer, perhaps I can set a globally accessible const (yuk)? But if that’s the case, this is a pattern often/always used, why not include it in the GAE environment? Being the common pattern I believe it is a mention in the documentation would improve matters.

Updating Entities

The issue which stumped me most was the updating of Entities. For example take these two data structures:

type Coinflip struct {
  Participants []Participant
  Head         string
  Tail         string
  Done         bool
}

type Participant struct {
   Email string
   Seen  datastore.Time
}

This was my first attempt which failed due to the fact that the Participants property of the Coinflip struct can not be stored in the datastore. I understand that enabling this would entail quite some magic. After some help on the mailing list I made it so that it stored a slice of pointers to keys; []*datastore.Key. Downside to this approach is that I need to write my own dereference function of this slice. Bummer, as I’m lightyears behind the average Go core member my dereference function is going to be far worse then one written by them. Now I manipulate one of the Participant by updating the Seen property (after finding it by iterating over the slice). Saving it back to the datastore requires a Key! So my current dereference function (fetchParticipants) now not only returns a slice of Participant but also a same length slice of Key. Having remembered the index of the iterator which I used to find the correct Participant I can now use that to find the associated Key and save the Entity. Why is this so convoluted? participant.Put() should have done it. I’m very much hoping that you are going to tell me that I’m a silly n00b and doing it thus and thus would be far easier. (Perhaps via a Query? I don’t quite grasp this yet.)

Random remarks

• Deployment is silly when compared to Heroku. $ git push heroku master and you’re done. I have my SSH private key on my computer so no need to auth every time (OK, once. When I first use my key, which is often in all kinds of projects).
• Documentation of the template lib is lacking. I chose to use the Mustache lib instead. That took very little time understanding while the template lib took too much time.
• Exuberant ctags doesn’t work with Go which is a shame, Vim just doesn’t work as well then. I found some efforts to fix this which are in dubious states. Probably gocode then, but that is yet an other tool raising the barrier to entry in my view.
• Rendering responses takes long long lines. For example: fmt.Fprint(w, mustache.RenderFile("./flipco.in/views/layout.html", map[string]string{"body":mustache.RenderFile("./flipco.in/views/home.html", map[string]string{"title":"Awesome coin tosses - Flipco.in", "nr_of_flips":fmt.Sprint(count)})})). This only has one type in the map if a collection is required things get even longer. But again, my inexperience might be to blame. Only recently I found out about the empty interface type which might be of use here.

Now it might seem that I have a lot of gripes with Go and GAE. There are also many things I like. Just to name a few, thus far I found nothing in the Go language I dislike and compared to maintain an own server GAE is great.