It doesn't actually use units. Everything is in nanoseconds, so time.Second is just another unitless number.

  const (
   Nanosecond  Duration = 1
   Microsecond          = 1000 * Nanosecond
   Millisecond          = 1000 * Microsecond
   Second               = 1000 * Millisecond
   Minute               = 60 * Second
   Hour                 = 60 * Minute
  )

Note that the wonderful Go type system interprets time.Second * time.Second as 277777h46m40s with the type time.Second (not sec^2)

  time.Second * time.Second

The type of this is `time.Duration` (or int64 internally), not `time.Second` (which is a const with a value).

I agree, though, that this is not quite sound, because it can be misused, as shown above with `time.Sleep(delaySecs * time.Second)`.

In Kotlin you can do `1.seconds + 1.minutes` but not `1.seconds * 1.minutes` (compilation error), which I quite like. Here is a playground link: https://pl.kotl.in/YZLu97AY8

Certainly, but for that the type system should be rich enough to support unit designators.

I know how to implement that in Haskell, and that it can be implemented in C++ and Rust. I know how to logically implement that in Java or Typescript, but usability will suck (no infix operators).

Go tends to cover such things by incorporating them directly in the language. But then it tends to not cover them at all because it would "overcomplicate" the language...

For a good example of what it looks like when somebody does bother to do it, see F# units of measure.