Middleware

mtgo has two middleware levels for different concerns:

Level	Method	Intercepts	Use case
Handler	UseMiddleware	Incoming update dispatch	Auth, logging, i18n, conversation state
Invoker	UseInvokerMiddleware	Outgoing RPC calls	Rate limiting, flood wait, logging, metrics

Handler Middleware

Wraps the handler chain. Lower priority number = runs first:

// Logging middleware (outermost)
client.UseMiddleware(func(next telegram.Handler) telegram.Handler {
    return &telegram.FuncHandler{Fn: func(ctx *telegram.Context) {
        if ctx.Message != nil {
            log.Printf("[%d] %s", ctx.Message.ChatID, ctx.Message.Text)
        }
        next.Handle(ctx)
    }}
}, -10) // priority -10 = outermost

// Auth guard
client.UseMiddleware(func(next telegram.Handler) telegram.Handler {
    return &telegram.FuncHandler{Fn: func(ctx *telegram.Context) {
        if ctx.Message != nil && ctx.Message.FromID != adminID {
            ctx.Reply("Unauthorized")
            ctx.Stopped = true
            return
        }
        next.Handle(ctx)
    }}
})

Invoker Middleware

Intercepts all outgoing Telegram API calls:

// Custom invoker middleware (e.g., force silent messages)
client.UseInvokerMiddleware(func(next tg.Invoker) tg.Invoker {
    return tg.InvokerFunc(func(ctx context.Context, input tg.TLObject, decode func(io.Reader) (tg.TLObject, error)) (tg.TLObject, error) {
        if req, ok := input.(*tg.MessagesSendMessageRequest); ok {
            req.Silent = true
            req.SetFlags()
        }
        return next.RPCInvoke(ctx, input, decode)
    })
})

Official Middlewares

Middleware	Level	Description
Flood Wait	Invoker	Auto-retry on FLOOD_WAIT errors
Rate Limit	Invoker	Token-bucket rate limiter

Writing Custom Middleware

Use the middleware template as a starting point for invoker middleware. Handler middleware can be written inline using FuncHandler.