Use run.sh.. This will show that underline conditions will cause err, and the errors will be low level. (Well a lower level than the fmt package, OS level.)

main.go

package main

import (
	"fmt"
	"log"
	"time"
)

func main() {
	log.SetFlags(log.Flags()|log.Lshortfile)
	for {
		time.Sleep(time.Second / 10)
		_, err := fmt.Println("Test line")
		if err != nil{
			log.Panic(err)
		}
	}
}

run.sh

#!/usr/bin/env bash
go run main.go | head