diff --git a/lib/slack.ex b/lib/slack.ex
index 2daf15c..bfa3630 100644
--- a/lib/slack.ex
+++ b/lib/slack.ex
@@ -93,13 +93,11 @@ defmodule Slack do
         }
       end
 
-      defoverridable [
-        handle_connect: 2,
-        handle_event: 3,
-        handle_close: 3,
-        handle_info: 3,
-        child_spec: 1
-      ]
+      defoverridable handle_connect: 2,
+                     handle_event: 3,
+                     handle_close: 3,
+                     handle_info: 3,
+                     child_spec: 1
     end
   end
 end
diff --git a/lib/slack/state.ex b/lib/slack/state.ex
index 5a5547f..53c36b3 100644
--- a/lib/slack/state.ex
+++ b/lib/slack/state.ex
@@ -53,7 +53,6 @@ defmodule Slack.State do
     put_in(slack, [:groups, channel.id], channel)
   end
 
-
   def update(%{type: "channel_left", channel: channel_id}, slack) do
     put_in(slack, [:channels, channel_id, :is_member], false)
   end
@@ -78,7 +77,13 @@ defmodule Slack.State do
     end
 
     def update(
-          %{type: "message", subtype: unquote(type <> "_topic"), channel: channel, user: user, topic: topic},
+          %{
+            type: "message",
+            subtype: unquote(type <> "_topic"),
+            channel: channel,
+            user: user,
+            topic: topic
+          },
           slack
         ) do
       put_in(slack, [unquote(plural_atom), safe_map_getter(channel), :topic], %{
@@ -92,14 +97,22 @@ defmodule Slack.State do
           %{type: "message", subtype: unquote(type <> "_join"), channel: channel, user: user},
           slack
         ) do
-      update_in(slack, [unquote(plural_atom), safe_map_getter(channel), safe_list_getter(:members)], &Enum.uniq([user | &1]))
+      update_in(
+        slack,
+        [unquote(plural_atom), safe_map_getter(channel), safe_list_getter(:members)],
+        &Enum.uniq([user | &1])
+      )
     end
 
     def update(
           %{type: "message", subtype: unquote(type <> "_leave"), channel: channel, user: user},
           slack
         ) do
-      update_in(slack, [unquote(plural_atom), safe_map_getter(channel), safe_list_getter(:members)], &(&1 -- [user]))
+      update_in(
+        slack,
+        [unquote(plural_atom), safe_map_getter(channel), safe_list_getter(:members)],
+        &(&1 -- [user])
+      )
     end
   end)
 
diff --git a/lib/slack/web/documentation.ex b/lib/slack/web/documentation.ex
index 6ceaf43..a058949 100644
--- a/lib/slack/web/documentation.ex
+++ b/lib/slack/web/documentation.ex
@@ -117,7 +117,7 @@ defmodule Slack.Web.Documentation do
       |> String.graphemes()
       |> Enum.reverse()
       |> Enum.find_index(&(&1 == "."))
-      |> (&(String.split_at(endpoint, -&1))).()
+      |> (&String.split_at(endpoint, -&1)).()
 
     {String.replace_suffix(module_name, ".", ""), function_name}
   end
diff --git a/mix.exs b/mix.exs
index 1aaa4cf..4f466e9 100644
--- a/mix.exs
+++ b/mix.exs
@@ -27,13 +27,13 @@ defmodule Slack.Mixfile do
 
   defp deps do
     [
-      {:httpoison, "~> 1.2"},
-      {:websocket_client, "~> 1.2.4"},
+      {:httpoison, "~> 1.8"},
+      {:websocket_client, "~> 1.4"},
       {:jason, "~> 1.1"},
       {:ex_doc, "~> 0.19", only: :dev},
-      {:credo, "~> 0.5", only: [:dev, :test]},
+      {:credo, "~> 1.6.4", only: [:dev, :test]},
       {:plug, "~> 1.6", only: :test},
-      {:cowboy, "~> 1.0.0", only: :test}
+      {:plug_cowboy, "~> 2.0", only: :test}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index b121288..d4ded27 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,26 +1,33 @@
 %{
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm", "7af5c7e09fe1d40f76c8e4f9dd2be7cebd83909f31fee7cd0e9eadc567da8353"},
-  "certifi": {:hex, :certifi, "2.3.1", "d0f424232390bf47d82da8478022301c561cf6445b5b5fb6a84d49a9e76d2639", [:rebar3], [{:parse_trans, "3.2.0", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm", "e12d667d042c11d130594bae2b0097e63836fe8b1e6d6b2cc48f8bb7a2cf7d68"},
-  "cowboy": {:hex, :cowboy, "1.0.4", "a324a8df9f2316c833a470d918aaf73ae894278b8aa6226ce7a9bf699388f878", [:make, :rebar], [{:cowlib, "~> 1.0.0", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "~> 1.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "6a0edee96885fae3a8dd0ac1f333538a42e807db638a9453064ccfdaa6b9fdac"},
-  "cowlib": {:hex, :cowlib, "1.0.2", "9d769a1d062c9c3ac753096f868ca121e2730b9a377de23dec0f7e08b1df84ee", [:make], [], "hexpm", "db622da03aa039e6366ab953e31186cc8190d32905e33788a1acb22744e6abd2"},
-  "credo": {:hex, :credo, "0.10.0", "66234a95effaf9067edb19fc5d0cd5c6b461ad841baac42467afed96c78e5e9e", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "893f53d5a5cb0bb6f96bde8732c20376e24be208fa052bdefd49119f77b64df6"},
+  "certifi": {:hex, :certifi, "2.9.0", "6f2a475689dd47f19fb74334859d460a2dc4e3252a3324bd2111b8f0429e7e21", [:rebar3], [], "hexpm", "266da46bdb06d6c6d35fde799bcb28d36d985d424ad7c08b5bb48f5b5cdd4641"},
+  "cowboy": {:hex, :cowboy, "2.9.0", "865dd8b6607e14cf03282e10e934023a1bd8be6f6bacf921a7e2a96d800cd452", [:make, :rebar3], [{:cowlib, "2.11.0", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "1.8.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "2c729f934b4e1aa149aff882f57c6372c15399a20d54f65c8d67bef583021bde"},
+  "cowboy_telemetry": {:hex, :cowboy_telemetry, "0.4.0", "f239f68b588efa7707abce16a84d0d2acf3a0f50571f8bb7f56a15865aae820c", [:rebar3], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "7d98bac1ee4565d31b62d59f8823dfd8356a169e7fcbb83831b8a5397404c9de"},
+  "cowlib": {:hex, :cowlib, "2.11.0", "0b9ff9c346629256c42ebe1eeb769a83c6cb771a6ee5960bd110ab0b9b872063", [:make, :rebar3], [], "hexpm", "2b3e9da0b21c4565751a6d4901c20d1b4cc25cbb7fd50d91d2ab6dd287bc86a9"},
+  "credo": {:hex, :credo, "1.6.4", "ddd474afb6e8c240313f3a7b0d025cc3213f0d171879429bf8535d7021d9ad78", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2.8", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "c28f910b61e1ff829bffa056ef7293a8db50e87f2c57a9b5c3f57eee124536b7"},
   "earmark": {:hex, :earmark, "1.3.1", "73812f447f7a42358d3ba79283cfa3075a7580a3a2ed457616d6517ac3738cb9", [:mix], [], "hexpm", "000aaeff08919e95e7aea13e4af7b2b9734577b3e6a7c50ee31ee88cab6ec4fb"},
-  "ex_doc": {:hex, :ex_doc, "0.19.3", "3c7b0f02851f5fc13b040e8e925051452e41248f685e40250d7e40b07b9f8c10", [:mix], [{:earmark, "~> 1.2", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.10", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm", "0e11d67e662142fc3945b0ee410c73c8c956717fbeae4ad954b418747c734973"},
-  "hackney": {:hex, :hackney, "1.13.0", "24edc8cd2b28e1c652593833862435c80661834f6c9344e84b6a2255e7aeef03", [:rebar3], [{:certifi, "2.3.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "5.1.2", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm", "4d605d33dd07ee1b82b105033cccb02379515105fceb1850746591814b00c205"},
-  "httpoison": {:hex, :httpoison, "1.2.0", "2702ed3da5fd7a8130fc34b11965c8cfa21ade2f232c00b42d96d4967c39a3a3", [:mix], [{:hackney, "~> 1.8", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "712d9b1dfde2470ed000dff4b2faddaf56d038e5ac1944abc0a81c901a368391"},
-  "idna": {:hex, :idna, "5.1.2", "e21cb58a09f0228a9e0b95eaa1217f1bcfc31a1aaa6e1fdf2f53a33f7dbd9494", [:rebar3], [{:unicode_util_compat, "0.3.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "8fddb3aec4692c71647d67de72536254bce9069851754e370a99f2aae69fbdf4"},
-  "jason": {:hex, :jason, "1.1.1", "d3ccb840dfb06f2f90a6d335b536dd074db748b3e7f5b11ab61d239506585eb2", [:mix], [{:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "639645cfac325e34938167b272bae0791fea3a34cf32c29525abf1d323ed4c18"},
-  "makeup": {:hex, :makeup, "0.8.0", "9cf32aea71c7fe0a4b2e9246c2c4978f9070257e5c9ce6d4a28ec450a839b55f", [:mix], [{:nimble_parsec, "~> 0.5.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "5fbc8e549aa9afeea2847c0769e3970537ed302f93a23ac612602e805d9d1e7f"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.13.0", "be7a477997dcac2e48a9d695ec730b2d22418292675c75aa2d34ba0909dcdeda", [:mix], [{:makeup, "~> 0.8", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "adf0218695e22caeda2820eaba703fa46c91820d53813a2223413da3ef4ba515"},
+  "earmark_parser": {:hex, :earmark_parser, "1.4.25", "2024618731c55ebfcc5439d756852ec4e85978a39d0d58593763924d9a15916f", [:mix], [], "hexpm", "56749c5e1c59447f7b7a23ddb235e4b3defe276afc220a6227237f3efe83f51e"},
+  "ex_doc": {:hex, :ex_doc, "0.28.4", "001a0ea6beac2f810f1abc3dbf4b123e9593eaa5f00dd13ded024eae7c523298", [:mix], [{:earmark_parser, "~> 1.4.19", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "bf85d003dd34911d89c8ddb8bda1a958af3471a274a4c2150a9c01c78ac3f8ed"},
+  "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},
+  "hackney": {:hex, :hackney, "1.18.1", "f48bf88f521f2a229fc7bae88cf4f85adc9cd9bcf23b5dc8eb6a1788c662c4f6", [:rebar3], [{:certifi, "~>2.9.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~>6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~>1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.3.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~>1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "a4ecdaff44297e9b5894ae499e9a070ea1888c84afdd1fd9b7b2bc384950128e"},
+  "httpoison": {:hex, :httpoison, "1.8.1", "df030d96de89dad2e9983f92b0c506a642d4b1f4a819c96ff77d12796189c63e", [:mix], [{:hackney, "~> 1.17", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "35156a6d678d6d516b9229e208942c405cf21232edd632327ecfaf4fd03e79e0"},
+  "idna": {:hex, :idna, "6.1.1", "8a63070e9f7d0c62eb9d9fcb360a7de382448200fbbd1b106cc96d3d8099df8d", [:rebar3], [{:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "92376eb7894412ed19ac475e4a86f7b413c1b9fbb5bd16dccd57934157944cea"},
+  "jason": {:hex, :jason, "1.3.0", "fa6b82a934feb176263ad2df0dbd91bf633d4a46ebfdffea0c8ae82953714946", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "53fc1f51255390e0ec7e50f9cb41e751c260d065dcba2bf0d08dc51a4002c2ac"},
+  "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
+  "makeup_elixir": {:hex, :makeup_elixir, "0.16.0", "f8c570a0d33f8039513fbccaf7108c5d750f47d8defd44088371191b76492b0b", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "28b2cbdc13960a46ae9a8858c4bebdec3c9a6d7b4b9e7f4ed1502f8159f338e7"},
+  "makeup_erlang": {:hex, :makeup_erlang, "0.1.1", "3fcb7f09eb9d98dc4d208f49cc955a34218fc41ff6b84df7c75b3e6e533cc65f", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "174d0809e98a4ef0b3309256cbf97101c6ec01c4ab0b23e926a9e17df2077cbb"},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
-  "mime": {:hex, :mime, "1.3.0", "5e8d45a39e95c650900d03f897fbf99ae04f60ab1daa4a34c7a20a5151b7a5fe", [:mix], [], "hexpm", "5e839994289d60326aa86020c4fbd9c6938af188ecddab2579f07b66cd665328"},
-  "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [:rebar3], [], "hexpm", "7a4c8e1115a2732a67d7624e28cf6c9f30c66711a9e92928e745c255887ba465"},
-  "nimble_parsec": {:hex, :nimble_parsec, "0.5.0", "90e2eca3d0266e5c53f8fbe0079694740b9c91b6747f2b7e3c5d21966bba8300", [:mix], [], "hexpm", "5c040b8469c1ff1b10093d3186e2e10dbe483cd73d79ec017993fb3985b8a9b3"},
-  "parse_trans": {:hex, :parse_trans, "3.2.0", "2adfa4daf80c14dc36f522cf190eb5c4ee3e28008fc6394397c16f62a26258c2", [:rebar3], [], "hexpm", "578b1d484720749499db5654091ddac818ea0b6d568f2c99c562d2a6dd4aa117"},
-  "plug": {:hex, :plug, "1.6.2", "e06a7bd2bb6de5145da0dd950070110dce88045351224bd98e84edfdaaf5ffee", [:mix], [{:cowboy, "~> 1.0.1 or ~> 1.1 or ~> 2.4", [hex: :cowboy, repo: "hexpm", optional: true]}, {:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}], "hexpm", "b2713c085797012661a6c10e1898a009f0cc2bae556cc00341b69600074c757b"},
+  "mime": {:hex, :mime, "2.0.2", "0b9e1a4c840eafb68d820b0e2158ef5c49385d17fb36855ac6e7e087d4b1dcc5", [:mix], [], "hexpm", "e6a3f76b4c277739e36c2e21a2c640778ba4c3846189d5ab19f97f126df5f9b7"},
+  "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm", "f278585650aa581986264638ebf698f8bb19df297f66ad91b18910dfc6e19323"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.2.3", "244836e6e3f1200c7f30cb56733fd808744eca61fd182f731eac4af635cc6d0b", [:mix], [], "hexpm", "c8d789e39b9131acf7b99291e93dae60ab48ef14a7ee9d58c6964f59efb570b0"},
+  "parse_trans": {:hex, :parse_trans, "3.3.1", "16328ab840cc09919bd10dab29e431da3af9e9e7e7e6f0089dd5a2d2820011d8", [:rebar3], [], "hexpm", "07cd9577885f56362d414e8c4c4e6bdf10d43a8767abb92d24cbe8b24c54888b"},
+  "plug": {:hex, :plug, "1.13.6", "187beb6b67c6cec50503e940f0434ea4692b19384d47e5fdfd701e93cadb4cc2", [:mix], [{:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.1.1 or ~> 1.2", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.3 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "02b9c6b9955bce92c829f31d6284bf53c591ca63c4fb9ff81dfd0418667a34ff"},
+  "plug_cowboy": {:hex, :plug_cowboy, "2.5.2", "62894ccd601cf9597e2c23911ff12798a8a18d237e9739f58a6b04e4988899fe", [:mix], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:cowboy_telemetry, "~> 0.3", [hex: :cowboy_telemetry, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm", "ea6e87f774c8608d60c8d34022a7d073bd7680a0a013f049fc62bf35efea1044"},
+  "plug_crypto": {:hex, :plug_crypto, "1.2.2", "05654514ac717ff3a1843204b424477d9e60c143406aa94daf2274fdd280794d", [:mix], [], "hexpm", "87631c7ad914a5a445f0a3809f99b079113ae4ed4b867348dd9eec288cecb6db"},
   "poison": {:hex, :poison, "4.0.1", "bcb755a16fac91cad79bfe9fc3585bb07b9331e50cfe3420a24bcc2d735709ae", [:mix], [], "hexpm", "ba8836feea4b394bb718a161fc59a288fe0109b5006d6bdf97b6badfcf6f0f25"},
-  "ranch": {:hex, :ranch, "1.6.0", "92ac674645ec5dd23c6f0aeb9fff0aae1dd4e94a0af8407ff4d14f750a4cd7cf", [:rebar3], [], "hexpm", "eb6170a697659046f517ceef15e568993d314591f05e73611e05605d4ac937f7"},
-  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [:make, :rebar], [], "hexpm", "4f8805eb5c8a939cf2359367cb651a3180b27dfb48444846be2613d79355d65e"},
-  "unicode_util_compat": {:hex, :unicode_util_compat, "0.3.1", "a1f612a7b512638634a603c8f401892afbf99b8ce93a45041f8aaca99cadb85e", [:rebar3], [], "hexpm", "da1d9bef8a092cc7e1e51f1298037a5ddfb0f657fe862dfe7ba4c5807b551c29"},
-  "websocket_client": {:hex, :websocket_client, "1.2.4", "14ec1ca4b6d247b44ccd9a80af8f6ca98328070f6c1d52a5cb00bc9d939d63b8", [:rebar3], [], "hexpm", "295a79cce15c208e03a545073f1318e97e7780aa9f2415e825cb9e338aecc305"},
+  "ranch": {:hex, :ranch, "1.8.0", "8c7a100a139fd57f17327b6413e4167ac559fbc04ca7448e9be9057311597a1d", [:make, :rebar3], [], "hexpm", "49fbcfd3682fab1f5d109351b61257676da1a2fdbe295904176d5e521a2ddfe5"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.6", "cf344f5692c82d2cd7554f5ec8fd961548d4fd09e7d22f5b62482e5aeaebd4b0", [:make, :mix, :rebar3], [], "hexpm", "bdb0d2471f453c88ff3908e7686f86f9be327d065cc1ec16fa4540197ea04680"},
+  "telemetry": {:hex, :telemetry, "1.1.0", "a589817034a27eab11144ad24d5c0f9fab1f58173274b1e9bae7074af9cbee51", [:rebar3], [], "hexpm", "b727b2a1f75614774cff2d7565b64d0dfa5bd52ba517f16543e6fc7efcc0df48"},
+  "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.0", "bc84380c9ab48177092f43ac89e4dfa2c6d62b40b8bd132b1059ecc7232f9a78", [:rebar3], [], "hexpm", "25eee6d67df61960cf6a794239566599b09e17e668d3700247bc498638152521"},
+  "websocket_client": {:hex, :websocket_client, "1.4.2", "f1036e3f9427eecdb66808eee56dbcaeb5a1a352306e6a0d0d23a9487205f4d7", [:rebar3], [], "hexpm", "c005e5f8f2f6a8533c497a509dc52f3e6fb42fa2e0d67bff8ebc8802868d84ed"},
 }
diff --git a/test/support/fake_slack.ex b/test/support/fake_slack.ex
index f014fc2..6979169 100644
--- a/test/support/fake_slack.ex
+++ b/test/support/fake_slack.ex
@@ -20,7 +20,7 @@ defmodule Slack.FakeSlack do
         :_,
         [
           {"/ws", Slack.FakeSlack.Websocket, []},
-          {:_, Plug.Adapters.Cowboy.Handler, {Slack.FakeSlack.Router, []}}
+          {:_, Plug.Cowboy.Handler, {Slack.FakeSlack.Router, []}}
         ]
       }
     ]
diff --git a/test/support/fake_slack/websocket.ex b/test/support/fake_slack/websocket.ex
index f3bf9d5..82639ab 100644
--- a/test/support/fake_slack/websocket.ex
+++ b/test/support/fake_slack/websocket.ex
@@ -1,37 +1,34 @@
 defmodule Slack.FakeSlack.Websocket do
-  @behaviour :cowboy_websocket_handler
+  @behaviour :cowboy_websocket
 
-  def init(_, _req, _opts) do
-    {:upgrade, :protocol, :cowboy_websocket}
+  @impl true
+  def init(req, state \\ %{}) do
+    {:cowboy_websocket, req, state}
   end
 
-  @activity_timeout 5000
-
-  def websocket_init(_type, req, _opts) do
-    state = %{}
-
+  @impl true
+  def websocket_init(state) do
     pid = Application.get_env(:slack, :test_pid)
     send(pid, {:websocket_connected, self()})
 
-    {:ok, req, state, @activity_timeout}
+    {:ok, state}
   end
 
-  def websocket_handle({:text, "ping"}, req, state) do
-    {:reply, {:text, "pong"}, req, state}
+  @impl true
+  def websocket_handle({:text, "ping"}, state) do
+    {:reply, {:text, "pong"}, state}
   end
 
-  def websocket_handle({:text, message}, req, state) do
+  @impl true
+  def websocket_handle({:text, message}, state) do
     pid = Application.get_env(:slack, :test_pid)
     send(pid, {:bot_message, Jason.decode!(message)})
 
-    {:ok, req, state}
-  end
-
-  def websocket_info(message, req, state) do
-    {:reply, {:text, message}, req, state}
+    {:ok, state}
   end
 
-  def websocket_terminate(_reason, _req, _state) do
-    :ok
+  @impl true
+  def websocket_info(message, state) do
+    {:reply, {:text, message}, state}
   end
 end