diff --git a/cmd/root.go b/cmd/root.go
index d6d7421..311953f 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -32,12 +32,13 @@ func NewRoot() (cmd *cobra.Command) {
 	flags.StringVarP(&opt.Output, "output", "o", "", "Write output to <file> instead of stdout.")
 	flags.BoolVarP(&opt.ShowProgress, "show-progress", "", true, "If show the progress of download")
 	flags.Int64VarP(&opt.ContinueAt, "continue-at", "", -1, "ContinueAt")
-	flags.IntVarP(&opt.Thread, "thread", "", 0, "")
+	flags.IntVarP(&opt.Thread, "thread", "t", 0,
+		`Download file with multi-threads. It only works when its value is bigger than 1`)
 	flags.BoolVarP(&opt.KeepPart, "keep-part", "", false,
 		"If you want to keep the part files instead of deleting them")
 	flags.StringVarP(&opt.Provider, "provider", "", ProviderGitHub, "The file provider")
-	flags.StringVarP(&opt.OS, "os", "", "", "The OS of target binary file")
-	flags.StringVarP(&opt.Arch, "arch", "", "", "The arch of target binary file")
+	flags.StringVarP(&opt.OS, "os", "", runtime.GOOS, "The OS of target binary file")
+	flags.StringVarP(&opt.Arch, "arch", "", runtime.GOARCH, "The arch of target binary file")
 
 	cmd.AddCommand(
 		getCmd,
@@ -115,14 +116,6 @@ func (o *downloadOption) preRunE(cmd *cobra.Command, args []string) (err error)
 		return fmt.Errorf("no URL provided")
 	}
 
-	if o.OS == "" {
-		o.OS = runtime.GOOS
-	}
-
-	if o.Arch == "" {
-		o.Arch = runtime.GOARCH
-	}
-
 	targetURL := args[0]
 	if !strings.HasPrefix(targetURL, "http://") && !strings.HasPrefix(targetURL, "https://") {
 		if targetURL, err = o.providerURLParse(targetURL); err != nil {
diff --git a/go.mod b/go.mod
index 92bd665..12576ea 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,7 @@ go 1.15
 require (
 	github.com/golang/mock v1.4.4
 	github.com/gosuri/uiprogress v0.0.1
-	github.com/linuxsuren/cobra-extension v0.0.9
+	github.com/linuxsuren/cobra-extension v0.0.10
 	github.com/onsi/ginkgo v1.14.2
 	github.com/onsi/gomega v1.10.4
 	github.com/spf13/cobra v1.1.1
diff --git a/go.sum b/go.sum
index 8a80a69..e83c2b9 100644
--- a/go.sum
+++ b/go.sum
@@ -162,6 +162,8 @@ github.com/linuxsuren/cobra-extension v0.0.6 h1:JlSmHjE/KCdJBZYGTjQbgvXSpziFwzpI
 github.com/linuxsuren/cobra-extension v0.0.6/go.mod h1:qcEJv7BbL0UpK6MbrTESP/nKf1+z1wQdMAnE1NBl3QQ=
 github.com/linuxsuren/cobra-extension v0.0.9 h1:VojTxx/eROco/fCatmz81L48gyy0AEPu1Tz6oFIaLak=
 github.com/linuxsuren/cobra-extension v0.0.9/go.mod h1:nDsXgvm0lSWVV+byAEfwhIGFDoIp0Sq9wkfNUDBp5do=
+github.com/linuxsuren/cobra-extension v0.0.10 h1:ciZDb2Bp/aAFqr4YoeVuH2uyBaBFfO6pwz1WBih7R4A=
+github.com/linuxsuren/cobra-extension v0.0.10/go.mod h1:nDsXgvm0lSWVV+byAEfwhIGFDoIp0Sq9wkfNUDBp5do=
 github.com/linuxsuren/http-downloader v0.0.2-0.20201207132639-19888a6beaec/go.mod h1:zRZY9FCDBuYNDxbI2Ny5suasZsMk7J6q9ecQ3V3PIqI=
 github.com/linuxsuren/http-downloader v0.0.6/go.mod h1:xxgh2OE7WGL9TwDE9L8Gh7Lqq9fFPuHbh5tofUitEfE=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=