Tee Writer - Write to two writers

tee_writer.go

package teewriter

type TeeWriter struct {
	w1 io.Writer
	w2 io.Writer
}

func (tw *TeeWriter) Write(p []byte) (n int, err error) {
	n1, err1 := tw.w1.Write(p)
	n2, err2 := tw.w2.Write(p)

	if err1 != err2 {
		return 0, fmt.Errorf("errors differ: %v and %v", err1, err2)
	}
	if n1 != n2 {
		return 0, fmt.Errorf("amts written differ: %v and %v", n1, n2)
	}
	return n1, err1
}