gnu: Add go-github-com-libp2p-go-flow-metrics.

* gnu/packages/golang.scm (go-github-com-libp2p-go-flow-metrics): New variable.

gnu/packages/golang.scm

@@ -2564,3 +2564,31 @@ generation features.  This code generation is used to achieve:
       (synopsis "XXX")
       (description "XXX")
       (license license:expat))))
+
+(define-public go-github-com-libp2p-go-flow-metrics
+  (let ((commit "7e5a55af485341567f98d6847a373eb5ddcdcd43")
+        (revision "0"))
+    (package
+      (name "go-github-com-libp2p-go-flow-metrics")
+      (version (git-version "0.2.0" revision commit))
+      (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+               (url "https://github.com/libp2p/go-flow-metrics.git")
+               (commit commit)))
+         (file-name (git-file-name name version))
+         (sha256
+          (base32
+           "1p87iyk6q6f3g3xkncssx400qlld8f2z93qiz8m1f97grfyhjif1"))))
+      (build-system go-build-system)
+      (arguments
+       `(#:import-path "github.com/libp2p/go-flow-metrics"
+         ;; TODO: Tests hang.
+         #:tests? #f))
+      (home-page
+       "https://github.com/libp2p/go-flow-metrics")
+      (synopsis "Simple library for tracking flow metrics")
+      (description "A simple alternative to rcrowley's @command{go-metrics}
+that's a lot faster (and only does simple bandwidth metrics).")
+      (license license:expat))))