ENV variables not coming through godotenv Docker - docker

Question

I have a web app written in Go, dockerised and using gomod.
I cannot get it to read environment variables.
Upon running docker-compose up always returns "Error getting env, not comming through"
I'm using godotenv to try do this. Below is my implementation. I cannot for the life of me figure out what's going wrong. If anyone can see something I'm missing you'll be saving a life.
The main.go, .env, docker-compose.yml and Dockerfile are all in the root of the project
main.go
func main() {
router := mux.NewRouter()
err := godotenv.Load()
if err != nil {
log.Fatalf("Error getting env, not comming through %v", err)
} else {
fmt.Println("We are getting the env values")
}
fmt.Println(os.Getenv("MY_ENV"))
}
.env
MY_ENV=thisismyenvvariable
DB_HOST=testdata123
DB_DRIVER=testdata123
DB_USER="testdata123"
DB_PASSWORD=testdata123
DB_NAME=testdata123
DB_PORT=5432
docker-compose.yml
version: '3'
services:
app:
container_name: template_123
build: .
ports:
- 8080:8080
restart: on-failure
volumes:
- api:/usr/src/app/
env_file:
- .env
depends_on:
- template-postgres
networks:
- template
template-postgres:
image: postgres:latest
container_name: startup_template_golang_db_postgres
environment:
- POSTGRES_USER=${DB_USER}
- POSTGRES_PASSWORD=${DB_PASSWORD}
- POSTGRES_DB=${DB_NAME}
- DATABASE_HOST=${DB_HOST}
ports:
- '5432:5432'
volumes:
- database_postgres:/var/lib/postgresql/data
env_file:
- .env
networks:
- template
pgadmin:
image: dpage/pgadmin4
container_name: pgadmin_container
environment:
PGADMIN_DEFAULT_EMAIL: ${PGADMIN_DEFAULT_EMAIL}
PGADMIN_DEFAULT_PASSWORD: ${PGADMIN_DEFAULT_PASSWORD}
depends_on:
- template-postgres
ports:
- "5050:80"
networks:
- template
restart: unless-stopped
volumes:
api:
database_postgres:
# Networks to be created to facilitate communication between containers
networks:
startup_template:
driver: bridge
Dockerfile
# Start from golang base image
FROM golang:alpine as builder
# ENV GO111MODULE=on
# Add Maintainer info
LABEL maintainer="satoshi123"
# Install git.
# Git is required for fetching the dependencies.
RUN apk update && apk add --no-cache git
# Set the current working directory inside the container
WORKDIR /app
# Copy go mod and sum files
COPY go.mod go.sum ./
# Download all dependencies. Dependencies will be cached if the go.mod and the go.sum files are not changed
RUN go mod download
# Copy the source from the current directory to the working Directory inside the container
COPY . .
# Build the Go app
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main .
# Start a new stage from scratch
FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /root/
# Copy the Pre-built binary file from the previous stage. Observe we also copied the .env file
COPY --from=builder /app/main .
# COPY --from=builder /app/.env .
# Expose port 8080 to the outside world
EXPOSE 8080
#Command to run the executable
CMD ["./main"]

Answer 1

If you're already using env_file in your docker_compose.yml, you don't really need godotenv, as the environment is already passed down from docker-compose:
version: '3'
services:
app:
image: busybox:latest
command: sh -c 'echo "Hello $$USER!"'
env_file:
- .env
# .env
USER=user1
$ docker-compose up
Recreating test_app_1 ... done
Attaching to test_app_1
app_1 | Hello user1!
test_app_1 exited with code 0
This is a better idea than trying to copy the .env file into the container, because it means you can pass environment variables without having to rebuild the container each time ;)
If you nonetheless want to use godotenv, I found that by simply uncommenting the COPY --from=builder /app/.env . line from your Dockerfile, the .env file gets loaded correctly (as godotenv finds it in the directory, whereas if it were commented it wouldn't).
$ docker-compose up
Starting template_123 ... done
Attaching to template_123
template_123 | We are getting the env values
template_123 | thisismyenvvariable
template_123 exited with code 0
If you want to keep it in sync with your filesystem, you will need to use a volume to link your .env with the one on your filesystem, or as I've said, ditch godotenv altogether as it is not really useful in your case.