update code after go mod update

builder/amazon/chroot/builder.go

@@ -102,7 +102,6 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 
 	// set default copy file if we're not giving our own
 	if b.config.CopyFiles == nil {
-		b.config.CopyFiles = make([]string, 0)
 		if !b.config.FromScratch {
 			b.config.CopyFiles = []string{"/etc/resolv.conf"}
 		}

builder/amazon/chroot/builder_test.go

@@ -159,7 +159,8 @@ func TestBuilderPrepare_CopyFilesNoDefault(t *testing.T) {
 	}
 
 	if len(b.config.CopyFiles) > 0 {
-		t.Errorf("Was expecting no default value for copy_files.")
+		t.Errorf("Was expecting no default value for copy_files. Found %v",
+			b.config.CopyFiles)
 	}
 }
 

post-processor/compress/post-processor.go

@@ -3,7 +3,6 @@ package compress
 import (
 	"archive/tar"
 	"archive/zip"
-	"compress/gzip"
 	"context"
 	"fmt"
 	"io"
@@ -273,8 +272,8 @@ func makeBGZFWriter(output io.WriteCloser, compressionLevel int) (io.WriteCloser
 
 func makeLZ4Writer(output io.WriteCloser, compressionLevel int) (io.WriteCloser, error) {
 	lzwriter := lz4.NewWriter(output)
-	if compressionLevel > gzip.DefaultCompression {
-		lzwriter.Header.HighCompression = true
+	if compressionLevel > 0 {
+		lzwriter.Header.CompressionLevel = compressionLevel
 	}
 	return lzwriter, nil
 }

website/source/docs/extending/plugins.html.md

@@ -160,7 +160,7 @@ using standard installation procedures.
 The specifics of how to implement each type of interface are covered in the
 relevant subsections available in the navigation to the left.
 
-\~> **Lock your dependencies!** Using `govendor` is highly recommended since
+\~> **Lock your dependencies!** Using `go mod` is highly recommended since
 the Packer codebase will continue to improve, potentially breaking APIs along
 the way until there is a stable release. By locking your dependencies, your
 plugins will continue to work with the version of Packer you lock to.