Logfatalf (#1990)

* bliep
Signed-off-by: Miek Gieben <miek@miek.nl>

* plugin/log: add log.Fatal[f]

Add log.Fatal(f) to mimic more of the log package. The first and only
use is in the (new) loop plugin.
Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/pkg/log/log.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	golog "log"
+	"os"
 )
 
 // D controls whether we should output debug logs. If true, we do.
@@ -62,12 +63,21 @@ func Error(v ...interface{}) { log(err, v...) }
 // Errorf is equivalent to log.Printf, but prefixed with "[ERROR] ".
 func Errorf(format string, v ...interface{}) { logf(err, format, v...) }
 
+// Fatal is equivalent to log.Print, but prefixed with "[FATAL] ", and calling
+// os.Exit(1).
+func Fatal(v ...interface{}) { log(fatal, v...); os.Exit(1) }
+
+// Fatalf is equivalent to log.Printf, but prefixed with "[FATAL] ", and calling
+// os.Exit(1)
+func Fatalf(format string, v ...interface{}) { logf(fatal, format, v...); os.Exit(1) }
+
 // Discard sets the log output to /dev/null.
 func Discard() { golog.SetOutput(ioutil.Discard) }
 
 const (
 	debug   = "[DEBUG] "
 	err     = "[ERROR] "
-	warning = "[WARNING] "
+	fatal   = "[FATAL] "
 	info    = "[INFO] "
+	warning = "[WARNING] "
 )