gnu: Add go-github-com-coreos-go-systemd-activation.

Required by restic-rest-server; see following commit.

* gnu/packages/golang.scm (go-github-com-coreos-go-systemd-activation):
New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu/packages/golang.scm

@@ -8964,6 +8964,29 @@ use one of our glamorous default themes.")
 It lets you parse and compare two semantic version strings.")
     (license license:asl2.0)))
 
+(define-public go-github-com-coreos-go-systemd-activation
+  (package
+    (name "go-github-com-coreos-go-systemd-activation")
+    (version "0.0.0-20191104093116-d3cd4ed1dbcf")
+    (source (origin
+              (method git-fetch)
+              (uri (git-reference
+                    (url "https://github.com/coreos/go-systemd")
+                    (commit (go-version->git-ref version))))
+              (file-name (git-file-name name version))
+              (sha256
+               (base32
+                "193mgqn7n4gbb8jb5kyn6ml4lbvh4xs55qpjnisaz7j945ik3kd8"))))
+    (build-system go-build-system)
+    (arguments
+     '(#:import-path "github.com/coreos/go-systemd/activation"
+       #:unpack-path "github.com/coreos/go-systemd"))
+    (home-page "https://github.com/coreos/go-systemd")
+    (synopsis "Go bindings to systemd socket activation")
+    (description "Go bindings to systemd socket activation; for writing and
+using socket activation from Go.")
+    (license license:asl2.0)))
+
 (define-public go-github-com-emirpasic-gods
   (package
     (name "go-github-com-emirpasic-gods")