fix: Replace std::time::Instant by wasm_timer::Instant

[fusetim]

Closes #2134
Needs tomaka/wasm-timer#17

• Just replaced the imports of std::time::Instant with wasm-timer::Instant for WASM support.
• Checked the existing uses of Instant, there is no dependency outside of the crate itself. All uses were never publicly exposed.
• I can't run the tests on my PC, it became really unstable when I tried but it fully compiled (even on wasm32 target using the Add missing methods to Instant, matching Rust 1.39 tomaka/wasm-timer#17).

[dvc94ch]

mdns won't work in a browser as it requires access to a udp socket. can you tell us more about what platform you're trying to run on?

[fusetim]

Yes you are right, in the case of mDNS it doesn't change anything, nevertheless we can think that some people could see the utility of using it with Node.js and in this case, Node.js has the capacity to open UDP sockets.

But in my case, it's about creating a custom node with a future protocol that I have to create, based on rust-libp2p and to be compiled with the target wasm32-unknown-unknown. It should run in the browser with some wasm-bindgen stuff.

I encountered an error with Gossipsub (when verifying messages) because it was using std::time::Instant::now() which is not implemented on the wasm32-unknown-unknown target today. In fact, I quickly went around to fix these imports and now it works perfectly following the changes made by this PR.

[mxinden]

In general, using wasm_timer across the project sounds good to me.

Yes you are right, in the case of mDNS it doesn't change anything, nevertheless we can think that some people could see the utility of using it with Node.js and in this case, Node.js has the capacity to open UDP sockets.

I would expect there to be additional blockers when using libp2p-mdns on Node.js. That said, I don't think it hurts to use wasm_timer in libp2p-mdns as well.

I left a comment on your wasm_timer pull request. Once that pull request is merged and released we can continue here.

Thanks for creating the patch @fusetim.

[dvc94ch]

believe this one was fixed by @wngr

[thomaseizinger]

believe this one was fixed by @wngr

Yep, thanks for the ping. Closing this.

[fusetim]

For tracking, fixed by #2245. Thanks.