Go can have weird behavior for nil - this illustrates one pitfal.

weird.go

package main

import (
	"fmt"
	"os"
)

func foo() error {
	err := &os.SyscallError{}
	err = nil
	return err
}

func main() {
	if err := foo(); err != nil {
		fmt.Printf("err is: %[1]p %[1]v (%[1]T)\n", err)
	}
}