env::set_var is marked unsafe now: https://doc.rust-lang.org/std/env/fn.set_var.html https://doc.rust-lang.org/std/env/fn.set_var.html And: > This function is

env::set_var is marked unsafe now: https://doc.rust-lang.org/std/env/fn.set_var.html https://doc.rust-lang.org/std/env/fn.set_var.html And: > This function is safe to call in a single-threaded program. > This function is also always safe to call on Windows, in single-threaded and multi-threaded programs. > In multi-threaded programs on other operating systems, the only safe option is to not use set_var or remove_var at all.