Add traceId to the response headers (#919)

* Add traceId to the request headers

* Add test cases

* Update refactor code

rest/handler/tracinghandler.go

@@ -21,6 +21,8 @@ func TracingHandler(next http.Handler) http.Handler {
 		defer span.Finish()
 		r = r.WithContext(ctx)
 
+		// Conveniently track error messages
+		w.Header().Set(trace.TraceIdKey, span.TraceId())
 		next.ServeHTTP(w, r)
 	})
 }

rest/handler/tracinghandler_test.go

@@ -1,6 +1,8 @@
 package handler
 
 import (
+	"github.com/tal-tech/go-zero/core/stringx"
+	"github.com/tal-tech/go-zero/core/trace"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -11,14 +13,19 @@ import (
 
 func TestTracingHandler(t *testing.T) {
 	req := httptest.NewRequest(http.MethodGet, "http://localhost", nil)
-	req.Header.Set("X-Trace-ID", "theid")
+
+	traceId := stringx.RandId()
+	req.Header.Set(trace.TraceIdKey, traceId)
+
 	handler := TracingHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		span, ok := r.Context().Value(tracespec.TracingKey).(tracespec.Trace)
 		assert.True(t, ok)
-		assert.Equal(t, "theid", span.TraceId())
+		assert.Equal(t, traceId, span.TraceId())
 	}))
 
 	resp := httptest.NewRecorder()
 	handler.ServeHTTP(resp, req)
+
 	assert.Equal(t, http.StatusOK, resp.Code)
+	assert.Equal(t, traceId, resp.Header().Get(trace.TraceIdKey))
 }