Error on trying to running mix phx.server on dev/prod

I tried to deploy to GCP (Cloud Run) with a Dockerfile, as:

FROM elixir:1.11.2-alpine AS builder

RUN apk --no-cache add build-base

WORKDIR /app

ARG MAILGUN_API_KEY
ARG MAILGUN_DOMAIN

ENV MAILGUN_DOMAIN=$MAILGUN_DOMAIN \
    MAILGUN_API_KEY=$MAILGUN_API_KEY

ENV MIX_ENV=prod

# Cache elixir deps
ADD mix.exs mix.lock ./
RUN mix local.rebar
RUN mix local.hex --force
RUN mix do deps.get, deps.compile

COPY ./lib ./lib
COPY ./config ./config
COPY ./priv ./priv

RUN mix release

FROM alpine:latest AS BANK

ARG DB_URL
ARG SECRET_KEY_BASE

ENV DB_URL=$DB_URL \
    SECRET_KEY_BASE=$SECRET_KEY_BASE

# Base packages
RUN apk --no-cache upgrade && \
    apk add --no-cache openssl \
    ncurses-libs postgresql-client

# Creates a non root user and creates artifact
RUN adduser -D -h home/app app
WORKDIR /home/app

COPY --from=builder /app/_build .
RUN chown -R app: ./prod
USER app

COPY ./entrypoint.sh ./

CMD ["/bin/sh", "entrypoint.sh"]

It builds correctly, but when try to forward traffic, it fails…

So I tried to run locally to see if there was any error, and:

** (Mix) Could not start application bank: Bank.Application.start(:normal, []) returned an error: shutdown: failed to start child: BankWeb.Endpoint
    ** (EXIT) an exception was raised:
        ** (FunctionClauseError) no function clause matching in Phoenix.Endpoint.Cowboy2Adapter.port_to_integer/1
            (phoenix 1.5.7) lib/phoenix/endpoint/cowboy2_adapter.ex:123: Phoenix.Endpoint.Cowboy2Adapter.port_to_integer(nil)
            (phoenix 1.5.7) lib/phoenix/endpoint/cowboy2_adapter.ex:63: anonymous fn/5 in Phoenix.Endpoint.Cowboy2Adapter.child_specs/2
            (elixir 1.11.0) lib/enum.ex:2181: Enum."-reduce/3-lists^foldl/2-0-"/3
            (phoenix 1.5.7) lib/phoenix/endpoint/cowboy2_adapter.ex:55: Phoenix.Endpoint.Cowboy2Adapter.child_specs/2
            (phoenix 1.5.7) lib/phoenix/endpoint/supervisor.ex:106: Phoenix.Endpoint.Supervisor.init/1
            (stdlib 3.13.2) supervisor.erl:301: :supervisor.init/1
            (stdlib 3.13.2) gen_server.erl:417: :gen_server.init_it/2
            (stdlib 3.13.2) gen_server.erl:385: :gen_server.init_it/6
            (stdlib 3.13.2) proc_lib.erl:226: :proc_lib.init_p_do_apply/3

Here are my configs files:

config.exs

# This file is responsible for configuring your application
# and its dependencies with the aid of the Mix.Config module.
#
# This configuration file is loaded before any dependency and
# is restricted to this project.

# General application configuration
use Mix.Config

config :bank,
  ecto_repos: [Bank.Repo],
  generators: [binary_id: true]

# Configures the endpoint
config :bank, BankWeb.Endpoint,
  url: [host: "localhost"],
  secret_key_base: "OrBd2a0fDrfuHkYprTerljuYWcFxr3O+MwVYcLIQVck9XTRMwDKOEig9CFH9h83D",
  render_errors: [view: BankWeb.ErrorView, accepts: ~w(json), layout: false],
  pubsub_server: Bank.PubSub,
  live_view: [signing_salt: "/+XhTad/"]

# Configures Elixir's Logger
config :logger, :console,
  format: "$time $metadata[$level] $message\n",
  metadata: [:request_id]

# Use Jason for JSON parsing in Phoenix
config :phoenix, :json_library, Jason

# Git Hooks
if Mix.env() == :dev do
  config :git_hooks,
    auto_install: true,
    verbose: true,
    hooks: [
      pre_commit: [
        tasks: [
          {:cmd, "mix format"},
          {:cmd, "mix compile --warning-as-errors"},
          {:cmd, "mix credo --strict"}
        ]
      ],
      pre_push: [
        verbose: false,
        tasks: [
          {:cmd, "mix dialyzer"},
          {:cmd, "mix test"}
        ]
      ]
    ]
end

# Mailing
config :bank,
  mailing_default_from_name: "Bank Live",
  mailing_default_from_email: "noreply@bank.com"

# Guardian
config :bank, BankWeb.Auth,
  issuer: "bank",
  secret_key: "U5Hu+z/iLlr8fz9jsgHSXVc4xd+TciR/aORxebMKGHp4vVB1tnmPBzI+V+IrbUti"

# Documenting
config :bank, Bank.Documenting,
  result_file_path: "README.md",
  default_response_transforms: %{
    inserted_at: "2021-01-04T22:16:56",
    updated_at: "2021-01-04T22:16:56",
    email: "valid@email.com"
  }

# Oban
# Configures Oban
config :bank, Oban,
  repo: Bank.Repo,
  plugins: [{Oban.Plugins.Pruner, max_age: 300}],
  queues: [default: 10, events: 50, media: 20, mailing: 50]

# Import environment specific config. This must remain at the bottom
# of this file so it overrides the configuration defined above.
import_config "#{Mix.env()}.exs"

prod.exs:

use Mix.Config

# Do not print debug messages in production
config :logger, level: :info

# Mailing
config :bank, Bank.Mailing,
  adapter: Bamboo.MailgunAdapter,
  api_key: System.get_env("MAILGUN_API_KEY"),
  domain: System.get_env("MAILGUN_DOMAIN")

config :bank, Bank.Endpoint, server: true

dev.exs:

use Mix.Config

# Configure your database
config :bank, Bank.Repo,
  username: "postgres",
  password: "postgres",
  database: "bank_dev",
  hostname: "localhost",
  show_sensitive_data_on_connection_error: true,
  pool_size: 10

# For development, we disable any cache and enable
# debugging and code reloading.
#
# The watchers configuration can be used to run external
# watchers to your application. For example, we use it
# with webpack to recompile .js and .css sources.
config :bank, BankWeb.Endpoint,
  http: [port: 4000],
  debug_errors: true,
  code_reloader: true,
  check_origin: false,
  watchers: []

# Do not include metadata nor timestamps in development logs
config :logger, :console, format: "[$level] $message\n"

# Set a higher stacktrace during development. Avoid configuring such
# in production as building large stacktraces may be expensive.
config :phoenix, :stacktrace_depth, 20

# Initialize plugs at runtime for faster development compilation
config :phoenix, :plug_init_mode, :runtime

# Mailing
config :bank, Bank.Mailing,
  adapter: Bamboo.LocalAdapter,
  open_email_in_browser_url: "http://localhost:4000/sent_emails"

runtime.exs:

import Config

secret_key_base = System.get_env("SECRET_KEY_BASE")

app_port = String.to_integer(System.get_env("PORT", "4000"))
app_hostname = System.get_env("HOST", "0.0.0.0")

db_url = System.get_env("DB_URL")
pool_size = String.to_integer(System.get_env("POOL_SIZE", "10"))

config :bank, Bank.Repo,
  adapter: Ecto.Adapters.Postgres,
  url: db_url,
  pool_size: pool_size,
  ssl: false

config :bank, BankWeb.Endpoint,
  load_from_system_env: true,
  http: [:inet6, port: {:system, "PORT"}],
  secret_key_base: secret_key_base

config :bank,
  app_port: app_port

config :bank,
  app_hostname: app_hostname

However, on production, it start normally, however I can’t access the app. What am I doing wrongly?