Update README.md

added missing imports

README.md

@@ -62,6 +62,8 @@ package main
 
 import (
     "fmt"
+    "os"
+    
     "github.com/Luxurioust/excelize"
 )
 
@@ -92,6 +94,8 @@ package main
 
 import (
     "fmt"
+    "os"
+    
     "github.com/Luxurioust/excelize"
 )