klog_file: workaround stdlib.user not supporting Nano Server

neolit123 · albertvaka · commit 466fbb6507db · 2020-03-10T10:30:28.000+01:00
user.Current() can panic on Windows if the OS is missing
netapi32.dll. This library is stripped from Windows Nano Server.

To workaround this, use environment variables on all versions
on Windows.
diff --git a/klog_file.go b/klog_file.go
@@ -24,6 +24,7 @@ import (
 	"os"
 	"os/user"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -55,13 +56,31 @@ func init() {
 		host = shortHostname(h)
 	}
 
-	current, err := user.Current()
-	if err == nil {
-		userName = current.Username
-	}
+	// On Windows, the Go 'user' package requires netapi32.dll.
+	// This affects Windows Nano Server:
+	//   https://github.com/golang/go/issues/21867
+	// Fallback to using environment variables.
+	if runtime.GOOS == "windows" {
+		u := os.Getenv("USERNAME")
+		if len(u) == 0 {
+			return
+		}
+		// Sanitize the USERNAME since it may contain filepath separators.
+		u = strings.Replace(u, `\`, "_", -1)
 
-	// Sanitize userName since it may contain filepath separators on Windows.
-	userName = strings.Replace(userName, `\`, "_", -1)
+		// user.Current().Username normally produces something like 'USERDOMAIN\USERNAME'
+		d := os.Getenv("USERDOMAIN")
+		if len(d) != 0 {
+			userName = d + "_" + u
+		} else {
+			userName = u
+		}
+	} else {
+		current, err := user.Current()
+		if err == nil {
+			userName = current.Username
+		}
+	}
 }
 
 // shortHostname returns its argument, truncating at the first period.
