code: func int64MultiplyScale1000(a int64) (int64, bool) {
  	if a == 0 || a == 1 {
  		return a * 1000, true
  	}
  	if a == mostNegative {
  		return 0, false
  	}
  	c := a * 1000
  	return c, c/1000 == a
  }
docs: // int64MultiplyScale1000 multiplies a by 1000, or returns false if that would overflow. This method is faster than
  // int64Multiply(a, 1000) because the compiler can optimize constant factor multiplication.