Feature: Add goctl env (#1557)

tools/goctl/pkg/downloader/downloader.go

@@ -0,0 +1,23 @@
+package downloader
+
+import (
+	"io"
+	"net/http"
+	"os"
+)
+
+func Download(url string, filename string) error {
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	f, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = io.Copy(f, resp.Body)
+	return err
+}