gnu: Add go-golang.org-x-sync-errgroup.

* gnu/packages/golang.scm (go-golang.org-x-sync-errgroup): New variable.

gnu/packages/golang.scm

@@ -3077,3 +3077,30 @@ alternative to @code{reflect.DeepEqual} for comparing whether two values
 are semantically equal in Go (for writing tests).")
     (home-page "https://godoc.org/github.com/google/go-cmp/cmp")
     (license license:asl2.0)))
+
+(define-public go-golang.org-x-sync-errgroup
+  (let ((commit "cd5d95a43a6e21273425c7ae415d3df9ea832eeb")
+        (revision "0"))
+    (package
+      (name "go-golang.org-x-sync-errgroup")
+      (version (git-version "0.0.0" revision commit))
+      (source (origin
+                (method git-fetch)
+                (uri (git-reference
+                       (url "https://go.googlesource.com/sync")
+                       (commit commit)))
+                (file-name (git-file-name name version))
+                (sha256
+                 (base32
+                  "1nqkyz2y1qvqcma52ijh02s8aiqmkfb95j08f6zcjhbga3ds6hds"))))
+      (build-system go-build-system)
+      (arguments
+       '(#:import-path "golang.org/x/sync/errgroup"
+         #:unpack-path "golang.org/x/sync"))
+      (synopsis "Synchronization, error propagation, and Context cancelation
+for groups of goroutines working on subtasks of a common task.")
+      (description "This package provides synchronization, error propagation,
+and Context cancelation for groups of goroutines working on subtasks of a
+common task.")
+      (home-page "https://godoc.org/golang.org/x/sync/errgroup")
+      (license license:bsd-3))))