add otel as separate module (#10)

Reviewed-on: #10
Co-authored-by: andrey <andrey@4devs.io>
Co-committed-by: andrey <andrey@4devs.io>

handler/otel/logger_example_test.go

@@ -0,0 +1,62 @@
+package otel_test
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"gitoa.ru/go-4devs/log"
+	"gitoa.ru/go-4devs/log/field"
+	"gitoa.ru/go-4devs/log/handler/otel"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/trace"
+)
+
+func ExampleNew_withTrace() {
+	ctx := context.Background()
+	logger := log.New(log.WithStdout()).With(otel.Middleware())
+
+	sctx, span := startSpan(ctx)
+
+	logger.Err(sctx, "log logrus")
+	logger.ErrKV(sctx, "log logrus kv", field.Int("int", 42))
+	logger.ErrKVs(sctx, "log logrus kv sugar", "err", io.EOF)
+
+	span.End()
+
+	// Output:
+	// msg="log logrus"
+	// msg="log logrus kv" int=42
+	// msg="log logrus kv sugar" err=EOF
+	// event: log logrus, SeverityText = ERROR, SeverityNumber = 17
+	// event: log logrus kv, SeverityText = ERROR, SeverityNumber = 17, int = 42
+	// event: log logrus kv sugar, SeverityText = ERROR, SeverityNumber = 17, err = EOF
+}
+
+func startSpan(ctx context.Context) (context.Context, trace.Span) {
+	tp := sdktrace.NewTracerProvider(sdktrace.WithSyncer(exporter{}))
+
+	return tp.Tracer("logger").Start(ctx, "operation")
+}
+
+type exporter struct{}
+
+func (e exporter) Shutdown(_ context.Context) error {
+	return nil
+}
+
+func (e exporter) ExportSpans(_ context.Context, spanData []sdktrace.ReadOnlySpan) error {
+	for _, data := range spanData {
+		for _, events := range data.Events() {
+			fmt.Print("event: ", events.Name)
+
+			for _, attr := range events.Attributes {
+				fmt.Printf(", %v = %v", attr.Key, attr.Value.AsInterface())
+			}
+
+			fmt.Print("\n")
+		}
+	}
+
+	return nil
+}