libgen-cli: install completions

pkgs/tools/misc/libgen-cli/default.nix

@@ -1,4 +1,4 @@
-{ lib, buildGoModule, fetchFromGitHub }:
+{ lib, buildGoModule, fetchFromGitHub, installShellFiles }:
 buildGoModule rec {
   pname = "libgen-cli";
   version = "1.0.6";
@@ -14,6 +14,15 @@ buildGoModule rec {
 
   subPackages = [ "." ];
 
+  nativeBuildInputs = [ installShellFiles ];
+
+  postInstall = ''
+    for shell in bash zsh; do
+      $out/bin/libgen-cli completion $shell > libgen-cli.$shell || :
+      installShellCompletion libgen-cli.$shell
+    done
+  '';
+
   meta = with lib; {
     homepage = "https://github.com/ciehanski/libgen-cli";
     description =