add http header option (#142)

* add http header option

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