refactor(CNV-47217): use golang gzip library

Use golang's gzip library directly from
the source code, in order to be able to
test this functionality as well.

Signed-off-by: Ben Oukhanov <[email protected]>

Author: codingben

Dockerfile

@@ -11,7 +11,7 @@ FROM quay.io/fedora/fedora-minimal:39
 RUN cd /usr/bin && \
     curl -L https://github.com/kubevirt/kubevirt/releases/download/v1.0.0/virtctl-v1.0.0-linux-amd64 --output virtctl && \
     chmod +x virtctl && \
-    microdnf install -y gzip qemu-img libguestfs-tools-c && \
+    microdnf install -y qemu-img libguestfs-tools-c && \
     microdnf clean all -y
 COPY --from=builder /app/kubevirt-disk-uploader /usr/local/bin/kubevirt-disk-uploader
 

main.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+	"compress/gzip"
 	"context"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"os/exec"
@@ -88,15 +90,35 @@ func downloadVirtualMachineDiskImage(vmName, volumeName string) error {
 func decompressVirtualMachineDiskImage() error {
 	log.Println("Decompressing downloaded disk image...")
 
-	cmd := exec.Command("gunzip", diskPath)
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
+	diskImg, err := os.Open(diskPath)
+	if err != nil {
+		return err
+	}
+	defer diskImg.Close()
 
-	if err := cmd.Run(); err != nil {
+	gzipReader, err := gzip.NewReader(diskImg)
+	if err != nil {
+		return err
+	}
+	defer gzipReader.Close()
+
+	newDiskImg, err := os.Create(diskPathDecompressed)
+	if err != nil {
+		return err
+	}
+	defer newDiskImg.Close()
+
+	_, err = io.Copy(newDiskImg, gzipReader)
+	if err != nil {
+		return err
+	}
+
+	err = os.Chmod(diskPathDecompressed, 0666) // Grants read and write permission to everyone.
+	if err != nil {
 		return err
 	}
 
-	log.Println("Decompressed completed successfully.")
+	log.Println("Decompression completed successfully.")
 	return nil
 }