all: replace some cases of strings.SplitN with strings.Cut (#28446)

rpc/json.go

@@ -86,8 +86,8 @@ func (msg *jsonrpcMessage) isUnsubscribe() bool {
 }
 
 func (msg *jsonrpcMessage) namespace() string {
-	elem := strings.SplitN(msg.Method, serviceMethodSeparator, 2)
-	return elem[0]
+	before, _, _ := strings.Cut(msg.Method, serviceMethodSeparator)
+	return before
 }
 
 func (msg *jsonrpcMessage) String() string {

rpc/service.go

@@ -93,13 +93,13 @@ func (r *serviceRegistry) registerName(name string, rcvr interface{}) error {
 
 // callback returns the callback corresponding to the given RPC method name.
 func (r *serviceRegistry) callback(method string) *callback {
-	elem := strings.SplitN(method, serviceMethodSeparator, 2)
-	if len(elem) != 2 {
+	before, after, found := strings.Cut(method, serviceMethodSeparator)
+	if !found {
 		return nil
 	}
 	r.mu.Lock()
 	defer r.mu.Unlock()
-	return r.services[elem[0]].callbacks[elem[1]]
+	return r.services[before].callbacks[after]
 }
 
 // subscription returns a subscription callback in the given service.