let the possibility to set the Host header

[juneil]

For our use case, we need to be able to set the Host header.
We are using a gateway that redirect to the right API based on the Host header.

[akanass]

Very important for us so if you merge this one ASAP it will be very nice and it's not a big change for you 👍

[akanass]

@theturtle32 when we can have this fix because it's very important for us and if we haven't it we'll need to migrate to another library.

Thanks for your collaboration.