http: port Go net/http timeout handling

[Darckfast]

This PR ports Go's net/http timeout feature to TinyGo allowing it to handle timeouts when using net/http e.g.

c := http.Client{
  Timeout: 2 * time.Second,
}

^ this will now return a timeout error if the request duration is longer than 2 seconds

This port is pretty much 1:1 to Go own timeout implementation, i removed parts that TInyGo doesnt support (they are commented with // TINYGO)

By bringing the Go net/http client .transport() function, it also fixes the issue where only roundTrip.go was used by default, even when compiling to wasm, where roundTrip_js.go should be used

Fixes #58
Fixes #66

I have wrote a wasm integration test , but i dont know how to go about it because it's inside test/wasm in the main repo, do i just open a PR in the main repo with it? or you guys suggest something else?

[b0ch3nski]

I have wrote a wasm integration test , but i dont know how to go about it because it's inside test/wasm in the main repo, do i just open a PR in the main repo with it? or you guys suggest something else?

Yes, please do so and maybe change net submodule to your branch so it can be tested together?

[0pcom]

Tested this against a real workload — the Skycoin daemon and web wallet, which use http.Client{Timeout: …} for peer/node queries — on the native (non-wasm) roundTrip.go path, combined with the host netdev from #59.

Confirmed it fixes the #58 crash: http.Client{Timeout}.Get() to an unreachable host now returns the dial error instead of panicking on the nil didTimeout. 👍

One thing worth flagging for the native path: the Timeout timer fires but doesn't actually abort an in-flight request. Against a server that sleeps 4s with a 1s client timeout, the call returns after the full ~4s with a nil error instead of timing out at ~1s:

T1 refused: true | connection refused        (crash fixed ✓)
T2 slow:   err=<nil> elapsed=4003ms          (want timeout ~1000ms)

setRequestCancel wires up req.Cancel/context and the timer correctly, but http/roundTrip.go (the native approximation of Transport.roundTrip) never observes req.Cancel/context/deadline and nothing sets a read deadline on the conn — so when the timer fires there's nothing to interrupt the read. On the wasm path roundTrip_js.go can cancel via the browser fetch, so this only affects the native path.

Not a blocker for this PR — fixing the crash is already a clear improvement. Just flagging that making Timeout actually cut off a slow response on native will additionally need roundTrip to honor cancellation (close the conn or set a read deadline when req.Cancel fires). Happy to help with that as a follow-up.