add http header option (#142)

* add http header option

handler.go

@@ -73,6 +73,7 @@ func (h *httpServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	ctx := context.WithValue(r.Context(), rspCodeKey{}, &rspCodeVal{})
+	ctx = context.WithValue(ctx, rspHeaderKey{}, &rspHeaderVal{})
 	md, ok := metadata.FromIncomingContext(ctx)
 	if !ok {
 		md = metadata.New(len(r.Header) + 8)
@@ -264,6 +265,13 @@ func (h *httpServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			w.Header().Set(k, v)
 		}
 	}
+	if md := getRspHeader(ctx); md != nil {
+		for k, v := range md {
+			for _, vv := range v {
+				w.Header().Add(k, vv)
+			}
+		}
+	}
 	if nct := w.Header().Get(metadata.HeaderContentType); nct != ct {
 		if cf, err = h.newCodec(nct); err != nil {
 			h.errorHandler(ctx, nil, w, r, err, http.StatusBadRequest)

options.go

@@ -38,6 +38,20 @@ type (
 	}
 )
 
+type (
+	rspHeaderKey struct{}
+	rspHeaderVal struct {
+		h http.Header
+	}
+)
+
+// SetRspHeader add response headers
+func SetRspHeader(ctx context.Context, h http.Header) {
+	if rsp, ok := ctx.Value(rspHeaderKey{}).(*rspHeaderVal); ok {
+		rsp.h = h
+	}
+}
+
 // SetRspCode saves response code in context, must be used by handler to specify http code
 func SetRspCode(ctx context.Context, code int) {
 	if rsp, ok := ctx.Value(rspCodeKey{}).(*rspCodeVal); ok {
@@ -45,6 +59,14 @@ func SetRspCode(ctx context.Context, code int) {
 	}
 }
 
+// getRspHeader get http.Header from context
+func getRspHeader(ctx context.Context) http.Header {
+	if rsp, ok := ctx.Value(rspHeaderKey{}).(*rspHeaderVal); ok {
+		return rsp.h
+	}
+	return nil
+}
+
 // GetRspCode used internally by generated http server handler
 func GetRspCode(ctx context.Context) int {
 	var code int