gnu: Add go-github-com-lestrrat-go-backoff-v2.

* gnu/packages/golang-xyz.scm (go-github-com-lestrrat-go-blackmagic-v2):
New variable.

Change-Id: Iaecc50f82e626f8237e2d33973ac7814be3add28
Modified-by: Sharlatan Hellseher <sharlatanus@gmail.com>
Signed-off-by: Sharlatan Hellseher <sharlatanus@gmail.com>

gnu/packages/golang-xyz.scm

@@ -12400,6 +12400,43 @@ the first isn't available.
 @end itemize")
     (license license:expat)))
 
+(define-public go-github-com-lestrrat-go-backoff-v2
+  (package
+    (name "go-github-com-lestrrat-go-backoff-v2")
+    (version "2.0.8")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+              (url "https://github.com/lestrrat-go/backoff")
+              (commit (string-append "v" version))))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32 "1s939szsdv0ggp69rig8dkl74s5dvwzm5cw80h0b3dvkqhikim5d"))))
+    (build-system go-build-system)
+    (arguments
+     (list
+      #:import-path "github.com/lestrrat-go/backoff"
+      #:phases
+      #~(modify-phases %standard-phases
+          (add-after 'unpack 'remove-benchmarks
+            (lambda* (#:key import-path #:allow-other-keys)
+              (delete-file-recursively
+               (string-append "src/" import-path "/bench")))))))
+    (native-inputs
+     (list go-github-com-stretchr-testify))
+    (propagated-inputs
+     (list go-github-com-lestrrat-go-option))
+    (home-page "https://github.com/lestrrat-go/backoff")
+    (synopsis "Idiomatic backoff for Golang")
+    (description
+     "This library is an implementation of
+@url{https://en.wikipedia.org/wiki/Exponential_backoff, backoff algorithm} for
+retrying operations.  It respects @code{context.Context} natively, and the
+critical notifications are done through channel operations, allowing you to
+write code that is both more explicit and flexibile.")
+    (license license:expat)))
+
 (define-public go-github-com-lestrrat-go-blackmagic
   (package
     (name "go-github-com-lestrrat-go-blackmagic")