otelgin: Add a WithSpanStartOptions option

CHANGELOG.md

@@ -21,6 +21,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Allow configuring samplers in `go.opentelemetry.io/contrib/otelconf`. (#7148)
 - Slog log bridge now sets `SeverityText` attribute using source value in `go.opentelemetry.io/contrib/bridges/otelslog`. (#7198)
 - Add `http.route` metric attribute in `go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin`. (#7275)
+- Add the `WithSpanStartOptions` option to add custom options to new spans `go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin`. (#7261)
 - Add instrumentation support for `go.mongodb.org/mongo-driver/v2` in `go.opentelemetry.io/contrib/instrumentation/go.mongodb.org/mongo-driver/v2/mongo/otelmongo`. (#6539)
 
 ### Changed

instrumentation/github.com/gin-gonic/gin/otelgin/config.go

@@ -21,6 +21,7 @@ import (
 type config struct {
 	TracerProvider       oteltrace.TracerProvider
 	Propagators          propagation.TextMapPropagator
+	SpanStartOptions     []oteltrace.SpanStartOption
 	Filters              []Filter
 	GinFilters           []GinFilter
 	SpanNameFormatter    SpanNameFormatter
@@ -89,6 +90,14 @@ func WithPropagators(propagators propagation.TextMapPropagator) Option {
 	})
 }
 
+// WithSpanStartOptions configures an additional set of
+// trace.SpanStartOptions, which are applied to each new span.
+func WithSpanStartOptions(opts ...oteltrace.SpanStartOption) Option {
+	return optionFunc(func(c *config) {
+		c.SpanStartOptions = append(c.SpanStartOptions, opts...)
+	})
+}
+
 // WithTracerProvider specifies a tracer provider to use for creating a tracer.
 // If none is specified, the global provider is used.
 func WithTracerProvider(provider oteltrace.TracerProvider) Option {

instrumentation/github.com/gin-gonic/gin/otelgin/gin.go

@@ -31,6 +31,7 @@ const (
 // server handling the request.
 func Middleware(service string, opts ...Option) gin.HandlerFunc {
 	cfg := config{}
+
 	for _, opt := range opts {
 		opt.apply(&cfg)
 	}
@@ -95,6 +96,8 @@ func Middleware(service string, opts ...Option) gin.HandlerFunc {
 			oteltrace.WithSpanKind(oteltrace.SpanKindServer),
 		}
 
+		opts = append(opts, cfg.SpanStartOptions...)
+
 		spanName := cfg.SpanNameFormatter(c)
 		if spanName == "" {
 			spanName = fmt.Sprintf("HTTP %s route not found", c.Request.Method)

instrumentation/github.com/gin-gonic/gin/otelgin/test/gin_test.go

@@ -268,6 +268,31 @@ func TestSpanStatus(t *testing.T) {
 	})
 }
 
+func TestWithSpanOptions_CustomAttributesAndSpanKind(t *testing.T) {
+	sr := tracetest.NewSpanRecorder()
+	provider := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr))
+
+	customAttr := attribute.String("custom.key", "custom.value")
+
+	router := gin.New()
+	router.Use(otelgin.Middleware("foobar",
+		otelgin.WithTracerProvider(provider),
+		otelgin.WithSpanStartOptions(trace.WithAttributes(customAttr)),
+	))
+	router.GET("/test", func(c *gin.Context) {})
+
+	r := httptest.NewRequest("GET", "/test", nil)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, r)
+
+	spans := sr.Ended()
+	require.Len(t, spans, 1)
+
+	span := spans[0]
+	assert.Contains(t, span.Attributes(), customAttr)
+	assert.Equal(t, trace.SpanKindServer, span.SpanKind())
+}
+
 func TestSpanName(t *testing.T) {
 	sr := tracetest.NewSpanRecorder()
 	provider := sdktrace.NewTracerProvider(