Final fix to handle situations where the current user is not available (

#194)

I finally found the circumstance where the current user info is not available. That happens if none of the environment variable $USER or $HOME are set and if cgo is disabled. That is the case when we build the release with Github Action.

So the previous fix solved only part of the problem. We can't presume that current user will always be available.

touch.go

@@ -9,14 +9,17 @@ import (
 	"time"
 )
 
-func getTouchFilename(image string) string {
-	usr := must(user.Current()).(*user.User)
+func getTouchFilename(image string) (string, error) {
+	usr, err := user.Current()
+	if err != nil {
+		return "", err
+	}
 	hash := sha1.Sum([]byte(image))
-	return filepath.Join(usr.HomeDir, ".tgf", base64.RawURLEncoding.EncodeToString(hash[:]))
+	return filepath.Join(usr.HomeDir, ".tgf", base64.RawURLEncoding.EncodeToString(hash[:])), nil
 }
 
 func getLastRefresh(image string) time.Time {
-	filename := getTouchFilename(image)
+	filename, _ := getTouchFilename(image)
 	if _, err := os.Stat(filename); err == nil {
 		// File exists
 		info := must(os.Stat(filename)).(os.FileInfo)
@@ -26,7 +29,10 @@ func getLastRefresh(image string) time.Time {
 }
 
 func touchImageRefresh(image string) {
-	filename := getTouchFilename(image)
+	filename, err := getTouchFilename(image)
+	if err != nil {
+		return
+	}
 	if _, err := os.Stat(filepath.Dir(filename)); os.IsNotExist(err) {
 		os.Mkdir(filepath.Dir(filename), 0755)
 	}