[chore] add headers to request

exporter/zipkinexporter/zipkin.go

@@ -78,6 +78,9 @@ func (ze *zipkinExporter) pushTraces(ctx context.Context, td ptrace.Traces) erro
 	if err != nil {
 		return fmt.Errorf("failed to push trace data via Zipkin exporter: %w", err)
 	}
+	for k, v := range ze.clientSettings.Headers {
+		req.Header.Set(k, string(v))
+	}
 	req.Header.Set("Content-Type", ze.serializer.ContentType())
 
 	resp, err := ze.client.Do(req)

exporter/zipkinexporter/zipkin_test.go

@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"go.opentelemetry.io/collector/config/configopaque"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -43,13 +44,13 @@ func TestZipkinExporter_roundtripJSON(t *testing.T) {
 	cst := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		s, _ := io.Copy(buf, r.Body)
 		sizes = append(sizes, s)
-		r.Body.Close()
 	}))
 	defer cst.Close()
 
 	cfg := &Config{
 		HTTPClientSettings: confighttp.HTTPClientSettings{
 			Endpoint: cst.URL,
+			Headers:  map[string]configopaque.String{"extra-header": "header-value"},
 		},
 		Format: "json",
 	}