My favorite little annoyance with Go is the way the := operator behaves with multiple assignment. It declares a new variable if there is no variable of that name in the current scope. But it refuses to do that if there are struct fields involved.

  var t int
  t, err := someFunc() // that's fine

but this doesn't compile:

  var s struct{ x int }
  s.x, err := someFunc() // doesn't compile