slog: only include for golang 1.21+

go.mod

@@ -313,4 +313,4 @@ require (
 	modernc.org/token v1.1.0 // indirect
 )
 
-go 1.21
+go 1.20

internal/log/slog.go

@@ -1,3 +1,5 @@
+//go:build go1.21
+
 package log
 
 import (

internal/log/slog_test.go

@@ -1,3 +1,5 @@
+//go:build go1.21
+
 package log
 
 import (

public/service/slog.go

@@ -0,0 +1,15 @@
+//go:build go1.21
+
+package service
+
+import (
+	"log/slog"
+
+	"github.com/benthosdev/benthos/v4/internal/log"
+)
+
+// SetLogger sets a customer logger via Go's standard logging interface,
+// allowing you to replace the default Benthos logger with your own.
+func (s *StreamBuilder) SetLogger(l *slog.Logger) {
+	s.customLogger = log.NewBenthosLogAdapter(l)
+}

public/service/stream_builder.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"log/slog"
 	"net/http"
 	"os"
 
@@ -126,12 +125,6 @@ func (s *StreamBuilder) SetPrintLogger(l PrintLogger) {
 	s.customLogger = log.Wrap(l)
 }
 
-// SetLogger sets a customer logger via Go's standard logging interface,
-// allowing you to replace the default Benthos logger with your own.
-func (s *StreamBuilder) SetLogger(l *slog.Logger) {
-	s.customLogger = log.NewBenthosLogAdapter(l)
-}
-
 // HTTPMultiplexer is an interface supported by most HTTP multiplexers.
 type HTTPMultiplexer interface {
 	HandleFunc(pattern string, handler func(http.ResponseWriter, *http.Request))