[dualogy]

> I did not know about sync/map at the time

Apparently also not about sync.Mutex =)

> if you want to use an interface you just have to implement all it's properties

You surely mean "methods" --- don't interfaces work like that everywhere they exist?

[terminalcommand]

I discovered Waitgroups during the project, but I have no formal training in concurrent programming, so it was a bit daunting for me. And as the error occured very rarely I could not be sure if using a mutex had solved my problem. But now I understand mutex was the way to go for accessing a shared resource.

As for the second point, sorry for the wrong wording, I meant "methods". But interfaces don't work like that everywhere they exist. For example in Java you explicitly use Class X implements Y, and if you do not implement all methods and properties, the compiler complains.

[dualogy]

> I discovered Waitgroups during the project

Don't know about your exact map use-case you had at hand, but generally speaking the Mutexes suffice for Lock()ing/Unlock()ing a resource that is accessed concurrently, whereas the WaitGroups serve usually best to just fire off a couple of parallel jobs (that don't access any shared-between-them resources) and then simply Wait() for them all to finish. No real protection from concurrent accesses in there, other than for the WaitGroup's own hidden internal counter that's used to Wait()

Of course these are the low-level sync primitives, channels are the higher-level abstraction, but the former can take you far --- sometimes the latter are the sanest/only choice of course. Especially for parallel goroutines needing to work with each other's intermediate results.

[fauigerzigerk]

Java interfaces don't have properties either (nor do Java classes), and you can explicitly state interface conformance in Go as well as others have explained elsewhere in this debate: https://news.ycombinator.com/item?id=15672619

What Java does have (since 8) is default method implementations in interfaces.

[terminalcommand]

Sorry, my fault. It seems in java you can declare constants in interfaces, but this is frowned upon.

  Interfaces cannot require instance variables to be defined -- only methods.
  (Variables can be defined in interfaces, but they do not behave as might be expected: they are treated as final static.)

(source: https://stackoverflow.com/questions/7311274/attributes-membe...)

(Another useful link explaining that statements resembling instance variables in interfaces are in fact constants: https://coderanch.com/t/178630/certification/Instance-variab...)