feat: got a better locked down version of rust

flake.nix

@@ -2,7 +2,7 @@
   description = "Skynet LDAP backend";
 
   inputs = {
-    nixpkgs.url = "nixpkgs/nixos-23.05";
+    nixpkgs.url = "nixpkgs/nixos-unstable";
     naersk.url  = "github:nix-community/naersk";
     utils.url   = "github:numtide/flake-utils";
   };
@@ -14,6 +14,7 @@
 
   outputs = { self, nixpkgs, utils, naersk }: utils.lib.eachDefaultSystem (system: 
   let
+    overrides = (builtins.fromTOML (builtins.readFile ./rust-toolchain.toml));
     pkgs            = nixpkgs.legacyPackages."${system}";
     naersk-lib      = naersk.lib."${system}";
     package_name    = "skynet_ldap_backend";
@@ -43,7 +44,15 @@
 
     # `nix develop`
     devShell = pkgs.mkShell {
-      nativeBuildInputs = with pkgs; [ rustc cargo pkg-config openssl];
+      nativeBuildInputs = with pkgs; [rustup rustPlatform.bindgenHook pkg-config openssl];
+      # libraries here
+      buildInputs = [ ];
+      RUSTC_VERSION = overrides.toolchain.channel;
+      # https://github.com/rust-lang/rust-bindgen#environment-variables
+      shellHook = ''
+        export PATH="''${CARGO_HOME:-~/.cargo}/bin":"$PATH"
+        export PATH="''${RUSTUP_HOME:-~/.rustup}/toolchains/$RUSTC_VERSION-${pkgs.stdenv.hostPlatform.rust.rustcTarget}/bin":"$PATH"
+      '';
     };
     
     nixosModule = { lib, pkgs, config, ... }: