A number of small improvements.

log.go

@@ -6,13 +6,22 @@ import (
 	"os"
 )
 
-var log = stdlog.New(os.Stderr, "", stdlog.LstdFlags)
+// BotLogger is an interface that represents the required methods to log data.
+//
+// Instead of requiring the standard logger, we can just specify the methods we
+// use and allow users to pass anything that implements these.
+type BotLogger interface {
+	Println(v ...interface{})
+	Printf(format string, v ...interface{})
+}
+
+var log BotLogger = stdlog.New(os.Stderr, "", stdlog.LstdFlags)
 
 // SetLogger specifies the logger that the package should use.
-func SetLogger(newLog *stdlog.Logger) error {
-	if newLog == nil {
+func SetLogger(logger BotLogger) error {
+	if logger == nil {
 		return errors.New("logger is nil")
 	}
-	log = newLog
+	log = logger
 	return nil
 }