Docker application not finding env var set in service's Variables tab

# syntax=docker/dockerfile:1

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Dockerfile reference guide at
# https://docs.docker.com/go/dockerfile-reference/

# Want to help us make this template better? Share your feedback here: https://forms.gle/ybq9Krt8jtBL3iCk7

ARG PYTHON_VERSION=3.11.7
ARG NODE_VERSION=18.17.1
FROM node:${NODE_VERSION}-alpine as build
WORKDIR /app
# RUN --mount=type=bind,source=package.json,target=package.json \
#     --mount=type=bind,source=yarn.lock,target=yarn.lock \
#     yarn install
COPY package.json yarn.lock ./
RUN yarn install
COPY . .
RUN yarn build

FROM python:${PYTHON_VERSION}-slim as base

# Prevents Python from writing pyc files.
ENV PYTHONDONTWRITEBYTECODE=1

# Keeps Python from buffering stdout and stderr to avoid situations where
# the application crashes without emitting any logs due to buffering.
ENV PYTHONUNBUFFERED=1

# Railway.app specifies the port we should listen on
# We default to 8000 in a local environment
ENV PORT=8000

WORKDIR /app

# Create a non-privileged user that the app will run under.
# See https://docs.docker.com/go/dockerfile-user-best-practices/
ARG UID=10001
RUN adduser \
    --disabled-password \
    --gecos "" \
    --home "/nonexistent" \
    --shell "/sbin/nologin" \
    --no-create-home \
    --uid "${UID}" \
    appuser

# Download dependencies as a separate step to take advantage of Docker's caching.
# Leverage a cache mount to /root/.cache/pip to speed up subsequent builds.
# Leverage a bind mount to requirements.txt to avoid having to copy them into
# into this layer.
RUN apt update && apt install -y --no-install-recommends libmagic-dev build-essential && rm -rf /var/lib/apt/lists/*
RUN pip install poetry

# RUN --mount=type=cache,id=s/2e9c673d-c965-440e-81a8-f03b0ad4a826-/pip-cache,target=/root/.cache/pip \
#     --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
#     --mount=type=bind,source=poetry.lock,target=poetry.lock \
#     poetry export -f requirements.txt --output requirements.txt && python -m pip install -r requirements.txt
COPY pyproject.toml poetry.lock ./
RUN poetry export -f requirements.txt --output requirements.txt && python -m pip install -r requirements.txt

# Switch to the non-privileged user to run the application.
USER appuser

# Copy the source code into the container.
COPY --from=build /app/build /app/build
COPY ./app /app/app
COPY ./public /app/public
# COPY .env /app/.env

# Expose the port that the application listens on.
EXPOSE $PORT

# Run the application.
CMD gunicorn app:app

# syntax=docker/dockerfile:1

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Dockerfile reference guide at
# https://docs.docker.com/go/dockerfile-reference/

# Want to help us make this template better? Share your feedback here: https://forms.gle/ybq9Krt8jtBL3iCk7

ARG PYTHON_VERSION=3.11.7
ARG NODE_VERSION=18.17.1
FROM node:${NODE_VERSION}-alpine as build
WORKDIR /app
# RUN --mount=type=bind,source=package.json,target=package.json \
#     --mount=type=bind,source=yarn.lock,target=yarn.lock \
#     yarn install
COPY package.json yarn.lock ./
RUN yarn install
COPY . .
RUN yarn build

FROM python:${PYTHON_VERSION}-slim as base

# Prevents Python from writing pyc files.
ENV PYTHONDONTWRITEBYTECODE=1

# Keeps Python from buffering stdout and stderr to avoid situations where
# the application crashes without emitting any logs due to buffering.
ENV PYTHONUNBUFFERED=1

# Railway.app specifies the port we should listen on
# We default to 8000 in a local environment
ENV PORT=8000

WORKDIR /app

# Create a non-privileged user that the app will run under.
# See https://docs.docker.com/go/dockerfile-user-best-practices/
ARG UID=10001
RUN adduser \
    --disabled-password \
    --gecos "" \
    --home "/nonexistent" \
    --shell "/sbin/nologin" \
    --no-create-home \
    --uid "${UID}" \
    appuser

# Download dependencies as a separate step to take advantage of Docker's caching.
# Leverage a cache mount to /root/.cache/pip to speed up subsequent builds.
# Leverage a bind mount to requirements.txt to avoid having to copy them into
# into this layer.
RUN apt update && apt install -y --no-install-recommends libmagic-dev build-essential && rm -rf /var/lib/apt/lists/*
RUN pip install poetry

# RUN --mount=type=cache,id=s/2e9c673d-c965-440e-81a8-f03b0ad4a826-/pip-cache,target=/root/.cache/pip \
#     --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
#     --mount=type=bind,source=poetry.lock,target=poetry.lock \
#     poetry export -f requirements.txt --output requirements.txt && python -m pip install -r requirements.txt
COPY pyproject.toml poetry.lock ./
RUN poetry export -f requirements.txt --output requirements.txt && python -m pip install -r requirements.txt

# Switch to the non-privileged user to run the application.
USER appuser

# Copy the source code into the container.
COPY --from=build /app/build /app/build
COPY ./app /app/app
COPY ./public /app/public
# COPY .env /app/.env

# Expose the port that the application listens on.
EXPOSE $PORT

# Run the application.
CMD gunicorn app:app