changed the behaviour on how default value is set

cli/main.go

@@ -71,7 +71,7 @@ func main() {
 	var logLevel string
 
 	flag.BoolVar(&globalImpl, "global-impl", false, "Record telemetry from the OpenTelemetry default global implementation")
-	flag.StringVar(&logLevel, "log-level", "info", "Define log visibility level")
+	flag.StringVar(&logLevel, "log-level", "", "Define log visibility level, default is `info`")
 
 	flag.Usage = usage
 	flag.Parse()
@@ -102,7 +102,9 @@ func main() {
 		instOptions = append(instOptions, auto.WithGlobal())
 	}
 
-	instOptions = append(instOptions, auto.WithLogLevel(logLevel))
+	if logLevel != "" {
+		instOptions = append(instOptions, auto.WithLogLevel(logLevel))
+	}
 
 	inst, err := auto.NewInstrumentation(ctx, instOptions...)
 	if err != nil {

instrumentation.go

@@ -361,9 +361,10 @@ var lookupEnv = os.LookupEnv
 //   - OTEL_SERVICE_NAME (or OTEL_RESOURCE_ATTRIBUTES): sets the service name
 //   - OTEL_TRACES_EXPORTER: sets the trace exporter
 //   - OTEL_GO_AUTO_GLOBAL: enables the OpenTelemetry global implementation
+//   - OTEL_LOG_LEVEL: sets the log level
 //
 // This option may conflict with [WithTarget], [WithPID], [WithTraceExporter],
-// [WithServiceName] and [WithGlobal] if their respective environment variable is defined.
+// [WithServiceName], [WithGlobal] and [WithLogLevel] if their respective environment variable is defined.
 // If more than one of these options are used, the last one provided to an
 // [Instrumentation] will be used.
 //