[asciimoo]

Interesting idea, how do you imagine a channel based API for this?

[hellcow]

I would ignore the GP's advice. Channels are prone to big errors -- panics and blocking -- which aren't detectable at compile time. They make sense to use internally but shouldn't be exposed in a public API. As one example, notice how the standard library's net/http package doesn't require you to use channels, but it uses them internally.

[JoeAcchino]

Would this work?

  c := colly.NewCollector()

  // this functions create a goroutine and returns a channel
  ch := c.HTML("a")  
  e := <- ch
  link := e.Attr("href")
  // ...

I'm a bit rusty (ah!) with go, so bear with me if the above contains errors.

[asciimoo]

How do you recognize if the collector has finished? If the site doesn't contain "a" elements (e.g. because of a network error), this example would block forever.

[maxpert]

This would work. No callback hell a pleasure for eyes!