I am new to phoenix and want to use it with gun to subscribe to websockets. But when I try this in a phoenix project, I get a dependency error. As a minimal example do the following:

$ mix phx.new --version
Phoenix v1.5.3
$ mix phx.new test --no-ecto
[...]

Then I add gun to the dependencies:

  defp deps do
    [
      {:phoenix, "~> 1.5.3"},
      {:phoenix_html, "~> 2.11"},
      {:phoenix_live_reload, "~> 1.2", only: :dev},
      {:phoenix_live_dashboard, "~> 0.2.0"},
      {:telemetry_metrics, "~> 0.4"},
      {:telemetry_poller, "~> 0.4"},
      {:gettext, "~> 0.11"},
      {:jason, "~> 1.0"},
      {:plug_cowboy, "~> 2.0"},
      {:gun, "~> 1.3.2"},
    ]
  end

But when I do mix deps.get I get the following error:

Resolving Hex dependencies...

Failed to use "cowlib" because
  gun (version 1.3.2) requires ~> 2.6.0
  mix.lock specifies 2.9.1

** (Mix) Hex dependency resolution failed, change the version requirements of your dependencies or unlock them (by using mix deps.update or mix deps.unlock). If you are unable to resolve the conflicts you can try overriding with {:dependency, "~> 1.0", override: true}

What should I do? Thanks in advance.