Update Poison dependency

Keep backwards compatibility since we do not actually _need_ Poison 2.x
yet.

1 files changed, 1 insertions, 1 deletions

diff --git a/mix.exs b/mix.exs
index f0771db..55e17e9 100644
--- a/mix.exs
+++ b/mix.exs
@@ -19,7 +19,7 @@ defmodule ExPrometheusIo.Mixfile do
   end
 
   defp deps do
-    [{:poison, "~> 1.5"}]
+    [{:poison, "~> 2.2 or ~> 1.5"}]
   end
 
   defp elixirc_paths(:test), do: ["lib", "test/support"]