seaweedfs: add version check passthru.tests

passthru.tests instead of installCheckPhase as recommended in
nix-community/nixpkgs-update#260 (comment)

Inspired by
https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/science/logic/key/default.nix#L54-L57

This is basically the extent of testing I usually do when an upgrade
is proposed, so this takes that manual step away.

pkgs/applications/networking/seaweedfs/default.nix

@@ -1,4 +1,9 @@
-{ lib, fetchFromGitHub, buildGoModule }:
+{ lib
+, fetchFromGitHub
+, buildGoModule
+, runCommand
+, seaweedfs
+}:
 
 buildGoModule rec {
   pname = "seaweedfs";
@@ -15,6 +20,11 @@ buildGoModule rec {
 
   subPackages = [ "weed" ];
 
+  passthru.tests.check-version = runCommand "weed-version" { meta.timeout = 3; } ''
+    ${seaweedfs}/bin/weed version | grep -Fw ${version}
+    touch $out
+  '';
+
   meta = with lib; {
     description = "Simple and highly scalable distributed file system";
     homepage = "https://github.com/chrislusf/seaweedfs";