My app crashes at the start

Questions & Help Questions
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39

Regardless of Phoenix version, if you are using Plug 1.7, then you will require {:plug_cowboy, "~> 1.0"} for cowboy to work.

If you are using Phoenix 1.4, then you can use {:plug_cowboy, "~> 2.0"} or {:plug_cowboy, "~> 1.0"}.

You should be prompted about this when the application starts:

warning: please add the following dependency to your mix.exs:

    {:plug_cowboy, "~> 1.0"}

This dependency is required by Plug.Adapters.Cowboy
which you may be using directly or indirectly.
Note you no longer need to depend on :cowboy directly.


[info] Application yolo123 exited: Yolo123.Application.start(:normal, []) returned an error: shutdown: failed to start child: Yolo123Web.Endpoint
    ** (EXIT) shutdown: failed to start child: Phoenix.Endpoint.Handler
        ** (EXIT) {%RuntimeError{message: "no plug_cowboy adapter"}, []}
** (Mix) Could not start application yolo123: Yolo123.Application.start(:normal, []) returned an error: shutdown: failed to start child: Yolo123Web.Endpoint
    ** (EXIT) shutdown: failed to start child: Phoenix.Endpoint.Handler
        ** (EXIT) {%RuntimeError{message: "no plug_cowboy adapter"}, []}