There are situations where a program will fail for good, and you want to have as much information about the failure as possible. In such difficult circumstances, you might consider using log.Panic(), which is the logging function that is illustrated in this section using the Go code of logPanic.go.

The Go code of logPanic.go follows:

package main 
 
import ( 
    "fmt" 
    "log" 
    "log/syslog" 
) 
 
func main() { 
    sysLog, err := syslog.New(syslog.LOG_ALERT|syslog.LOG_MAIL, 
 "Some program!") 
    if err != nil { 
        log.Fatal(err) 
    } else { 
        log.SetOutput(sysLog) 
    } 
 
    log.Panic(sysLog) 
    fmt.Println("Will you see this?") 
} 

Executing logPanic.go on macOS High Sierra will produce the following output:

$ go run logPanic.go
panic: &{17 Some program! iMac.local   {0 0} 0xc42000c220}
  
goroutine 1 [running]:
log.Panic(0xc42004ff50, 0x1, 0x1)
    /usr/local/Cellar/go/1.9.1/libexec/src/log/log.go:330 +0xc0
main.main()
    /Users/mtsouk/Desktop/masterGo/ch/ch1/code/logPanic.go:17 +0xea
exit status 2

Running the same program on a Debian Linux machine with Go version 1.3.3 will generate the following output:

$ go run logPanic.go
panic: &{17 Some program! mail   {0 0} 0xc2080400e0}
    
goroutine 16 [running]:
runtime.panic(0x4ec360, 0xc208000320)
    /usr/lib/go/src/pkg/runtime/panic.c:279 +0xf5
log.Panic(0xc208055f20, 0x1, 0x1)
    /usr/lib/go/src/pkg/log/log.go:307 +0xb6
main.main()
    /home/mtsouk/Desktop/masterGo/ch/ch1/code/logPanic.go:17 +0x169
  
goroutine 17 [runnable]:
runtime.MHeap_Scavenger()
    /usr/lib/go/src/pkg/runtime/mheap.c:507
runtime.goexit()
    /usr/lib/go/src/pkg/runtime/proc.c:1445
    
goroutine 18 [runnable]:
bgsweep()
    /usr/lib/go/src/pkg/runtime/mgc0.c:1976
runtime.goexit()
    /usr/lib/go/src/pkg/runtime/proc.c:1445
    
goroutine 19 [runnable]:
runfinq()
    /usr/lib/go/src/pkg/runtime/mgc0.c:2606
runtime.goexit()
    /usr/lib/go/src/pkg/runtime/proc.c:1445
exit status 2

The output of log.Panic() includes additional low-level information that will hopefully help you resolve difficult and rare situations that happen in your Go code.

Analogous to the log.Fatal() function, the use of the log.Panic() function will add an entry to the proper log file and will immediately terminate the Go program.