Accessing std.Io instance in deep functions

[compact ore]

How can i access std.Io instance in deep functions. I know that i can access via init.io in main function. but if i need to access std.Io instance in deep functions, should I need to pass it to every function i call? furthermore this also applies to other instances in std.process.Init

Accessing std.Io instance in deep functions

[tropic mortar]

either pass it deeply or (in application/non-library code only) you could use global vars. the former approach is more friendly for unit tests though

although, unit tests doing io might be weird regardless

[compact ore]

can you give an example for using "global vars" ?

[nocturne tinsel]

something like this, its a very bad practice to do if this is library logic though since the application can no longer control the io instance.
the "correct" answer is yes pass it as a argument to each function

const std = @import("std");

var IoImpl: std.Io = undefined;

pub fn main() !void {
    const alloc = std.heap.smp_allocator;
    var threaded = std.Io.Threaded.init(alloc, .{});
    IoImpl = threaded.io();
    _ = IoImpl;
}

fn otherFunc() !void {
    _ = IoImpl; // used here!
}