1. Create empty Erlang release and application with Rebar3

	$ rebar3 new release cowboy_hello_world 

	$ cd cowboy_hello_world


2. Make changes to automatically generated rebar.config 

	$ vi rebar.config 

	2.1. Add Cowboy dependency to deps section of rebar.config 
		{deps, [
		        {cowboy, {git, "https://github.com/ninenines/cowboy", {branch, "master"}}}
		]}.

	2.2. Add rebar3_run dependency to plugins section of rebar.config 
		{plugins, [rebar3_run]}.


3. Add reference to Cowboy in application description file

	$ vi apps/cowboy_hello_world/src/cowboy_hello_world.app.src

		{applications,
		   [kernel,
		    stdlib,
		    cowboy
		]},


4. Register a handler for the / url

	$ vi apps/cowboy_hello_world/src/cowboy_hello_world_app.erl  

	start(_Type, _Args) ->
	        Dispatch = cowboy_router:compile([
	                {'_', [
	                        {"/", toppage_handler, []}
	                ]}
	        ]),
	        {ok, _} = cowboy:start_clear(http, [{port, 8080}], #{
	                env => #{dispatch => Dispatch}
	        }),
	        cowboy_hello_world_sup:start_link().


5. And create handle referenced above

	$ vi apps/cowboy_hello_world/src/toppage_handler.erl

	-module(toppage_handler).

	-export([init/2]).

	init(Req0, Opts) ->
	        Req = cowboy_req:reply(200, #{
	                <<"content-type">> => <<"text/plain">>
	        }, <<"Hello world!">>, Req0),
	        {ok, Req, Opts}.


6. Compile

	$ rebar3 compile


7. Run

	$ rebar3 shell

	Open http://localhost:8080 in browser


8. Clean 

	$ rebar3 clean; rm -rf _build rebar.lock


9. Create release

	$ rebar3 release


10. Start release

	$ _build/default/rel/cowboy_hello_world/bin/cowboy_hello_world console
	
	Open http://localhost:8080 in browser