close(connClosed)
		return nil
	}

	inWrite := make(chan bool, 1)
	var errConnClosed = errors.New("conn closed for test")
	conn.writeFunc = func(p []byte) (n int, err error) {
		inWrite <- true
		<-connClosed
		return 0, errConnClosed
	}

	closeReturned := make(chan bool, 1)
	go func() {
		<-inWrite
		tconn.Close() // test that this doesn't block forever.
		closeReturned <- true

		x = f(x)
	}
	GlobalF = x
}

func BenchmarkSqrtGoLatency(b *testing.B) {
	x := 10.0
	for i := 0; i < b.N; i++ {
		x = SqrtGo(x)
	}
	GlobalF = x
}

func isPrime(i int) bool {
	// Yes, this is a dumb way to write this code,
	// but calling Sqrt repeatedly in this way demonstrates
	// the benefit of using a direct SQRT instruction on systems