Changing out rng as input to DH keying material

Question

I am currently creating some DH keys using the x25519-dalek-ng crate for it.

Using rand_core I can create them like this, with the OSrng:

use x25519_dalek_ng::{self,PublicKey, StaticSecret};
use rand_core::{OsRng};
fn main() {
        let i_dh_privkey : StaticSecret  = StaticSecret::new(OsRng);
        let i_dh_public_key = PublicKey::from(&i_dh_privkey);
}

But I want to change to a different rng, one that does not require a OS. So I wanted to shift to rand_chacha. I then tried doing this:

use x25519_dalek_ng::{self,PublicKey, StaticSecret};
use rand_chacha::{ChaCha8Rng};
fn main() {
        let i_dh_privkey : StaticSecret  = StaticSecret::new(ChaCha8Rng);
        let i_dh_public_key = PublicKey::from(&i_dh_privkey);
}

And rust doesnt like this, and says:

help: use struct literal syntax instead'

Which I don't really udnerstand, both OSrng and ChaCha8Rng are structs.

StaticSecret::new() takes anything that implements crpytorng, should I do something to implement that for the chacha rng?