Go: What we got right, what we got wrong(commandcenter.blogspot.com)

   var MyError = errors.New("my error")

   if (err == MyError) {
      // We got MyError!
   }

   type MyError struct {
      Code int
      User User
      // ...
   }

   // Error is needed to satisfy the error interface.
   func (m MyError) Error() string {
      return fmt.Sprintf("code %d caused by %s", m.Code, m.User.Name)
   }

   func doSomething(user User) error {
      return MyError{Code: 1, User: user}
   }

    for (item in collection) {
        ...
    }

    list.map { it + 1 }

    fun printAll(vararg strings: String)

    constructor(...)

    companion object