$ n /tmp/x.go
    1   package main
    2   
    3   import "runtime"
    4   
    5   func main() {
    6       var file string
    7       var line int
    8       func() {
    9           defer func() {
   10               _, file, line, _ = runtime.Caller(1)
   11           }()
   12       }()
   13       println(file, line)
   14   }
$ go1.4 run /tmp/x.go
/tmp/x.go 12
$ go1.5 run /tmp/x.go
/tmp/x.go 12
$ go1.6 run /tmp/x.go
/tmp/x.go 12
$ go run /tmp/x.go
/tmp/x.go 8
$ 

$ n /tmp/x.go
    1   package main
    2   
    3   import (
    4       "os"
    5       "runtime"
    6   )
    7   
    8   func main() {
    9       var file string
   10       var line int
   11       func() {
   12           defer func() {
   13               _, file, line, _ = runtime.Caller(1)
   14           }()
   15           if len(os.Args) > 1 {
   16               return
   17           }
   18           return
   19       }()
   20       println(file, line)
   21   }
$ go1.6 run /tmp/x.go
/tmp/x.go 18
$ go1.6 run /tmp/x.go -
/tmp/x.go 16
$ go run /tmp/x.go
/tmp/x.go 18
$ go run /tmp/x.go -
/tmp/x.go 16
$