The use of the infinitive when an imperative is required is a common error that unfortunately nowadays is spreading all around, and it happens with all verbs in imperative form in colloquial speech in Spain and other countries where the form vosotros is used in enclitic form (-os) with an imperative.
From RAE FAQ
It is not considered proper, in careful speech, the use of the infinitive
instead of the imperative to address an order to a plural second person
as is often done in colloquial speech:
No se considera correcto, en el habla esmerada, el uso del infinitivo
en lugar del imperativo para dirigir una orden a una segunda persona
del plural, como se hace a menudo en el habla coloquial:
- ¡×Venir aquí ahora mismo, granujas! (Venid)
- ×Poneros el pijama y ×dormiros cuanto antes. (Poneos/dormíos)
It is only valid to use the infinitive with imperative value addressing a
singular or plural second person when it is preceded by the preposition a,
proper use of the colloquial spoken language.
Solo es válido el empleo del infinitivo con valor de imperativo
dirigido a una segunda persona del singular o del plural cuando
aparece precedido de la preposición a, uso propio de la lengua oral
coloquial.
- ¡Tú, a callar!
- Niños, a dormir
The same for ir. Use of iros, irse,... when used as imperative, is a mistake.
Also, every verb in imperative loses the last -d when adding the enclitic -os.
- poned + vosotros = poned + os = poneos
with the exception of ir, which does not lose the final -d (idos). Even then, many people use the arcaic and incorrect form ×íos (the correct imperative without the final -d by comparison with other imperatives when using the enclitic -os).
There is a complete page dedicated to the verb ir in RAE archives. This is an excerpt:
Las formas de imperativo propias de este verbo son ve (tú) e id
(vosotros) y, para los usos pronominales, vete (tú) e idos (vosotros)
Debe evitarse, para el imperativo singular, el uso de la forma vulgar
×ves y, para el imperativo plural, el uso del infinitivo ×iros y el de
la forma arcaica ×íos.
The proper imperative forms of this verb are ve (tú) and id
(vosotros) and, for the pronominal uses, vete (tú) and idos (vosotros)
It should be avoided, for the singular imperative, to use the vulgar form
×ves and, for the plural imperative, to use the infinitive ×iros and the
*archaic form* ×íos.