code: func ParMap(f, xs interface{}) interface{} {
  	n := runtime.NumCPU()
  	if n < 1 {
  		n = 1
  	}
  	return ParMapN(f, xs, n)
  }
docs: // ParMap has a parametric type:
  //
  //	func ParMap(f func(A) B, xs []A) []B
  //
  // ParMap is just like Map, except it applies `f` to each element in `xs`
  // concurrently using N worker goroutines (where N is the number of CPUs
  // available reported by the Go runtime). If you want to control the number
  // of goroutines spawned, use `ParMapN`.
  //
  // It is important that `f` not be a trivial operation, otherwise the overhead
  // of executing it concurrently will result in worse performance than using
  // a `Map`.