Wait for Postgres initialization in Docker-Compose

docker-compose.yml

version: '3.8'

services:
  todo-app:
    build: ./
    command: ./wait-for-postgres.sh db ./todo-app
    ports:
      - 8000:8000
    depends_on:
      - db
    environment:
      - DB_PASSWORD=qwerty

  db:
    restart: always
    image: postgres:latest
    volumes:
    - ./.database/postgres/data:/var/lib/postgresql/data
    environment:
      - POSTGRES_PASSWORD=qwerty
    ports:
      - 5436:5432

Dockerfile

FROM golang:1.14-buster

RUN go version
ENV GOPATH=/

COPY ./ ./

# install psql
RUN apt-get update
RUN apt-get -y install postgresql-client

# make wait-for-postgres.sh executable
RUN chmod +x wait-for-postgres.sh

# build go app
RUN go mod download
RUN go build -o todo-app ./cmd/main.go

CMD ["./todo-app"]

wait-for-postgres.sh

#!/bin/sh
# wait-for-postgres.sh

set -e

host="$1"
shift
cmd="$@"

until PGPASSWORD=$DB_PASSWORD psql -h "$host" -U "postgres" -c '\q'; do
  >&2 echo "Postgres is unavailable - sleeping"
  sleep 1
done

>&2 echo "Postgres is up - executing command"
exec $cmd