fix #182. remove access_token when navigating page result

go.mod

@@ -1,3 +1,3 @@
 module github.com/huandu/facebook/v2
 
-go 1.12
+go 1.13

paging_result.go

@@ -114,6 +114,10 @@ func (pr *PagingResult) navigate(url *string) (noMore bool, err error) {
 	params := Params{}
 	pr.session.prepareParams(params)
 
+	// Per #182, access_token is always useless.
+	// As we may need to keep other params, do a manual delete here.
+	delete(params, "access_token")
+
 	if len(params) == 0 {
 		pagingURL = *url
 	} else {

params.go

@@ -175,7 +175,7 @@ func isEmptyValue(v reflect.Value) bool {
 //
 // Encode may panic if Params contains values that cannot be marshalled to json string.
 func (params Params) Encode(writer io.Writer) (mime string, err error) {
-	if params == nil || len(params) == 0 {
+	if len(params) == 0 {
 		mime = mimeFormURLEncoded
 		return
 	}