support go 1.20+ (#608)

.github/workflows/go_test.yml

@@ -12,6 +12,7 @@ jobs:
     strategy:
       matrix:
         go-version:
+          - "1.20"
           - "1.21"
     name: lint and test
     runs-on: ubuntu-latest

example_test.go

@@ -2,7 +2,6 @@ package gocron_test
 
 import (
 	"fmt"
-	"log/slog"
 	"sync"
 	"time"
 
@@ -550,7 +549,7 @@ func ExampleWithLocation() {
 func ExampleWithLogger() {
 	_, _ = NewScheduler(
 		WithLogger(
-			NewJSONSlogLogger(slog.LevelInfo),
+			NewLogger(LogLevelDebug),
 		),
 	)
 }

go.mod

@@ -1,6 +1,6 @@
 module github.com/go-co-op/gocron/v2
 
-go 1.21
+go 1.20
 
 require (
 	github.com/google/uuid v1.4.0

job.go

@@ -5,13 +5,13 @@ import (
 	"errors"
 	"fmt"
 	"math/rand"
-	"slices"
 	"strings"
 	"time"
 
 	"github.com/google/uuid"
 	"github.com/jonboulle/clockwork"
 	"github.com/robfig/cron/v3"
+	"golang.org/x/exp/slices"
 )
 
 // internalJob stores the information needed by the scheduler

logger.go

@@ -1,8 +1,7 @@
 package gocron
 
 import (
-	"log/slog"
-	"os"
+	"log"
 )
 
 // Logger is the interface that wraps the basic logging methods
@@ -12,56 +11,67 @@ import (
 // or implement your own Logger. The actual level of Log that is logged
 // is handled by the implementation.
 type Logger interface {
-	Debug(msg string, args ...any)
-	Error(msg string, args ...any)
-	Info(msg string, args ...any)
-	Warn(msg string, args ...any)
+	Debug(msg string, args ...interface{})
+	Error(msg string, args ...interface{})
+	Info(msg string, args ...interface{})
+	Warn(msg string, args ...interface{})
 }
 
 var _ Logger = (*noOpLogger)(nil)
 
 type noOpLogger struct{}
 
-func (l noOpLogger) Debug(_ string, _ ...any) {}
-func (l noOpLogger) Error(_ string, _ ...any) {}
-func (l noOpLogger) Info(_ string, _ ...any)  {}
-func (l noOpLogger) Warn(_ string, _ ...any)  {}
+func (l noOpLogger) Debug(_ string, _ ...interface{}) {}
+func (l noOpLogger) Error(_ string, _ ...interface{}) {}
+func (l noOpLogger) Info(_ string, _ ...interface{})  {}
+func (l noOpLogger) Warn(_ string, _ ...interface{})  {}
 
-var _ Logger = (*slogLogger)(nil)
+var _ Logger = (*logger)(nil)
 
-type slogLogger struct {
-	sl *slog.Logger
-}
+// LogLevel is the level of logging that should be logged
+// when using the basic NewLogger.
+type LogLevel int
 
-func NewJSONSlogLogger(level slog.Level) Logger {
-	return NewSlogLogger(
-		slog.New(
-			slog.NewJSONHandler(
-				os.Stdout,
-				&slog.HandlerOptions{
-					Level: level,
-				},
-			),
-		),
+const (
+	LogLevelError LogLevel = iota
+	LogLevelWarn
+	LogLevelInfo
+	LogLevelDebug
 )
+
+type logger struct {
+	level LogLevel
 }
 
-func NewSlogLogger(sl *slog.Logger) Logger {
-	return &slogLogger{sl: sl}
+// NewLogger returns a new Logger that logs at the given level.
+func NewLogger(level LogLevel) Logger {
+	return &logger{level: level}
 }
 
-func (l *slogLogger) Debug(msg string, args ...any) {
-	l.sl.Debug(msg, args...)
+func (l *logger) Debug(msg string, args ...interface{}) {
+	if l.level < LogLevelDebug {
+		return
+	}
+	log.Printf("DEBUG: %s, %v\n", msg, args)
 }
 
-func (l *slogLogger) Error(msg string, args ...any) {
-	l.sl.Error(msg, args...)
+func (l *logger) Error(msg string, args ...interface{}) {
+	if l.level < LogLevelError {
+		return
+	}
+	log.Printf("ERROR: %s, %v\n", msg, args)
 }
 
-func (l *slogLogger) Info(msg string, args ...any) {
-	l.sl.Info(msg, args...)
+func (l *logger) Info(msg string, args ...interface{}) {
+	if l.level < LogLevelInfo {
+		return
+	}
+	log.Printf("INFO: %s, %v\n", msg, args)
 }
 
-func (l *slogLogger) Warn(msg string, args ...any) {
-	l.sl.Warn(msg, args...)
+func (l *logger) Warn(msg string, args ...interface{}) {
+	if l.level < LogLevelWarn {
+		return
+	}
+	log.Printf("WARN: %s, %v\n", msg, args)
 }

scheduler.go

@@ -3,11 +3,11 @@ package gocron
 import (
 	"context"
 	"reflect"
-	"slices"
 	"time"
 
 	"github.com/google/uuid"
 	"github.com/jonboulle/clockwork"
+	"golang.org/x/exp/slices"
 )
 
 var _ Scheduler = (*scheduler)(nil)

scheduler_test.go

@@ -3,7 +3,6 @@ package gocron
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"sync"
 	"testing"
 	"time"
@@ -16,7 +15,7 @@ import (
 func newTestScheduler(options ...SchedulerOption) (Scheduler, error) {
 	// default test options
 	out := []SchedulerOption{
-		WithLogger(NewJSONSlogLogger(slog.LevelDebug)),
+		WithLogger(NewLogger(LogLevelDebug)),
 		WithStopTimeout(time.Second),
 	}
 

util.go

@@ -3,12 +3,12 @@ package gocron
 import (
 	"context"
 	"reflect"
-	"slices"
 	"sync"
 	"time"
 
 	"github.com/google/uuid"
 	"golang.org/x/exp/maps"
+	"golang.org/x/exp/slices"
 )
 
 func callJobFuncWithParams(jobFunc any, params ...any) error {