Go: Check Nil interface the right way.go

```go
func isNil(i interface{}) bool {                        
   return i == nil || reflect.ValueOf(i).IsNil()                       
}
```

better:

```go
func isNilFixed(i interface{}) bool {
   if i == nil {
      return true
   }
   switch reflect.TypeOf(i).Kind() {
   case reflect.Ptr, reflect.Map, reflect.Array, reflect.Chan, reflect.Slice:
      return reflect.ValueOf(i).IsNil()
   }
   return false
}
```