shutdown_timeout setter on HttpServer

[gh0st-work]

There is pretty configurable param shutdown_timeout on HttpServer.builder, but pub setter on HttpServer struct/impl is missing.

Just need to copy from builder this pub method to HttpServer:

/// Workers still alive after the timeout are force dropped.
///
/// By default shutdown timeout sets to 30 seconds.
pub fn shutdown_timeout(mut self, secs: u64) -> Self {
    self.shutdown_timeout = Duration::from_secs(secs);
    self
}

And change self.shutdown_timeout to self.builder.shutdown_timeout ofc

Im not pretty sure about that (infrastructure is huge), so in format of issue. U can use this issue as a note)))

BTW, thx for the project

[fakeshadow]

Thanks for the issue. You are right the issue template is missing and your format is good.
As for the timeout API PR is welcomed.