cmd/internal/bio: remove unused MustWriter

Change-Id: Ic3064f636ecd1953c0a95a74eaaf886ac6f1a83c

src/cmd/internal/bio/must.go

@@ -1,43 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package bio
-
-import (
-	"io"
-	"log"
-)
-
-// MustClose closes Closer c and calls log.Fatal if it returns a non-nil error.
-func MustClose(c io.Closer) {
-	if err := c.Close(); err != nil {
-		log.Fatal(err)
-	}
-}
-
-// MustWriter returns a Writer that wraps the provided Writer,
-// except that it calls log.Fatal instead of returning a non-nil error.
-func MustWriter(w io.Writer) io.Writer {
-	return mustWriter{w}
-}
-
-type mustWriter struct {
-	w io.Writer
-}
-
-func (w mustWriter) Write(b []byte) (int, error) {
-	n, err := w.w.Write(b)
-	if err != nil {
-		log.Fatal(err)
-	}
-	return n, nil
-}
-
-func (w mustWriter) WriteString(s string) (int, error) {
-	n, err := io.WriteString(w.w, s)
-	if err != nil {
-		log.Fatal(err)
-	}
-	return n, nil
-}