app.ex

Mix.install([
  {:ecto_sql, "~> 3.7.0"},
  {:myxql, "~> 0.6.2"}
])

Application.put_env(:foo, Repo, database: "app_db",
                                hostname: "db",
                                username: "app_user",
                                password: "app_pass")

defmodule Repo do
  use Ecto.Repo,
    adapter: Ecto.Adapters.MyXQL,
    otp_app: :foo
end

defmodule Migration0 do
  use Ecto.Migration

  def change do
    create table("things") do
      add(:thing_time, :time)
      add(:thing_time_usec, :time_usec)
      add(:thing_naive_datetime, :naive_datetime)
      add(:thing_naive_datetime_usec, :naive_datetime_usec)
      add(:thing_utc_datetime, :utc_datetime)
      add(:thing_utc_datetime_usec, :utc_datetime_usec)
    end
  end
end

defmodule Thing do
  use Ecto.Schema
  import Ecto.Changeset

  schema "things" do
    field(:thing_time, :time)
  end

  def changeset(thing, params \\ %{}) do
    thing
    |> cast(params, [
      :thing_time,
    ])
    |> validate_required([
      :thing_time,
    ])
  end
end

defmodule Main do
  def main do
    children = [
      Repo
    ]

    _ = Repo.__adapter__().storage_down(Repo.config())
    :ok = Repo.__adapter__().storage_up(Repo.config())

    {:ok, _} = Supervisor.start_link(children, strategy: :one_for_one)

    current_time = ~T[00:00:00]
    Ecto.Migrator.run(Repo, [{0, Migration0}], :up, all: true, log_sql: :debug)
    Repo.insert!(%Thing{
      thing_time: current_time,
    })

    IO.inspect(Repo.all(Thing))
  end
end

Main.main()

docker-compose.yml

version: '3'
services:
  db:
    platform: linux/x86_64
    image: mysql:5.7.38
    environment:
      MYSQL_ROOT_PASSWORD: root_pass
      MYSQL_DATABASE: app_db
      MYSQL_USER: app_user
      MYSQL_PASSWORD: app_pass
    ports:
      - "3306:3306"
  app:
    build: .
    command: elixir app/app.ex
    volumes:
      - .:/app
    depends_on:
      - db

Dockerfile

FROM hexpm/elixir:1.13.4-erlang-24.3.4.2-debian-stretch-20210902

RUN apt-get update && \
    apt-get install -y postgresql-client && \
    mix local.hex --force && \
    mix local.rebar --force

ENV APP_HOME /app
RUN mkdir $APP_HOME
WORKDIR $APP_HOME