Update bzip2.go remove depend bzip2 or bzip2.exe

bzip2.go

@@ -1,40 +1,26 @@
 package binarydist
 
 import (
+	"github.com/dsnet/compress/bzip2"
 	"io"
-	"os/exec"
 )
-
 type bzip2Writer struct {
-	c *exec.Cmd
-	w io.WriteCloser
+	w io.Writer
+	r *bzip2.Writer
 }
-
-func (w bzip2Writer) Write(b []byte) (int, error) {
-	return w.w.Write(b)
+func (w *bzip2Writer) Write(b []byte) (int, error) {
+	return w.r.Write(b)
 }
-
-func (w bzip2Writer) Close() error {
-	if err := w.w.Close(); err != nil {
+func (w *bzip2Writer) Close() error {
+	err := w.r.Close()
+	if err != nil {
 		return err
 	}
-	return w.c.Wait()
+	// Since the underlying writer is the one we passed in, we don't need to
+	// close it again; it's the responsibility of the caller to close it.
+	return nil
 }
-
-// Package compress/bzip2 implements only decompression,
-// so we'll fake it by running bzip2 in another process.
-func newBzip2Writer(w io.Writer) (wc io.WriteCloser, err error) {
-	var bw bzip2Writer
-	bw.c = exec.Command("bzip2", "-c")
-	bw.c.Stdout = w
-
-	if bw.w, err = bw.c.StdinPipe(); err != nil {
-		return nil, err
-	}
-
-	if err = bw.c.Start(); err != nil {
-		return nil, err
-	}
-
-	return bw, nil
+func newBzip2Writer(w io.Writer) (io.WriteCloser, error) {
+	r ,err:= bzip2.NewWriter(w,nil)
+	return &bzip2Writer{w: w, r: r}, err
 }