journald: don't call Enabled before each write (#407)

Enabled opens and close a socket connection by reusing or initializing
a global connection.

I also updated go-systemd to the current development release to include
the following fix:

coreos/go-systemd@75f33b0

This is the only journal related change since the latest stable release

go.mod

@@ -3,7 +3,7 @@ module github.com/rs/zerolog
 go 1.15
 
 require (
-	github.com/coreos/go-systemd/v22 v22.3.2
+	github.com/coreos/go-systemd/v22 v22.3.3-0.20220203105225-a9a7ef127534
 	github.com/mattn/go-colorable v0.1.12
 	github.com/pkg/errors v0.9.1
 	github.com/rs/xid v1.3.0

go.sum

@@ -1,5 +1,7 @@
 github.com/coreos/go-systemd/v22 v22.3.2 h1:D9/bQk5vlXQFZ6Kwuu6zaiXJ9oTPe68++AzAJc1DzSI=
 github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
+github.com/coreos/go-systemd/v22 v22.3.3-0.20220203105225-a9a7ef127534 h1:rtAn27wIbmOGUs7RIbVgPEjb31ehTVniDwPGXyMxm5U=
+github.com/coreos/go-systemd/v22 v22.3.3-0.20220203105225-a9a7ef127534/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/mattn/go-colorable v0.1.12 h1:jF+Du6AlPIjs2BiUiQlKOX0rt3SujHxPnksPKZbaA40=
 github.com/mattn/go-colorable v0.1.12/go.mod h1:u5H1YNBxpqRaxsYJYSkiCWKzEfiAb1Gb520KVy5xxl4=

journald/journald.go

@@ -1,3 +1,4 @@
+//go:build !windows
 // +build !windows
 
 // Package journald provides a io.Writer to send the logs
@@ -69,19 +70,14 @@ func levelToJPrio(zLevel string) journal.Priority {
 }
 
 func (w journalWriter) Write(p []byte) (n int, err error) {
-	if !journal.Enabled() {
-		err = fmt.Errorf("cannot connect to journalD")
-		return
-	}
-
 	var event map[string]interface{}
 	origPLen := len(p)
 	p = cbor.DecodeIfBinaryToBytes(p)
 	d := json.NewDecoder(bytes.NewReader(p))
 	d.UseNumber()
 	err = d.Decode(&event)
 	jPrio := defaultJournalDPrio
-	args := make(map[string]string, 0)
+	args := make(map[string]string)
 	if err != nil {
 		return
 	}
@@ -100,9 +96,9 @@ func (w journalWriter) Write(p []byte) (n int, err error) {
 			continue
 		}
 
-		switch value.(type) {
+		switch v := value.(type) {
 		case string:
-			args[jKey], _ = value.(string)
+			args[jKey] = v
 		case json.Number:
 			args[jKey] = fmt.Sprint(value)
 		default: