os/errno:fix os.Errno 's nil pointer derefer in linux

_demo/checkfile/demo.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+func main() {
+	tempDir := os.TempDir()
+	noexist := filepath.Join(tempDir, "noexist.txt")
+
+	if _, err := os.Stat(noexist); err != nil {
+		if os.IsNotExist(err) {
+			fmt.Println("noexist:", err.Error())
+		} else {
+			fmt.Println("exist,other err:", err.Error())
+		}
+	}
+
+	if _, err := os.Open(noexist); err != nil {
+		if os.IsNotExist(err) {
+			fmt.Println("noexist:", err.Error())
+		} else {
+			fmt.Println("exist,other err:", err.Error())
+		}
+	}
+}