failed to load .env file but still gets the environment variables

That's the code segment where I load .env file and set the variables.

// init executes the initial configuration.
func init() {
    // loads the file for env. variables
    if err := godotenv.Load(".env"); err != nil {
        log.Printf("failed to load env file: %v\n", err)
    }

    // env variables are set based values within the .env file.
    os.Setenv("dbname", os.Getenv("DB_NAME"))
    os.Setenv("username", os.Getenv("DB_USERNAME"))
    os.Setenv("pw", os.Getenv("DB_PASSWORD"))
    os.Setenv("dbport", os.Getenv("DB_PORT"))
    os.Setenv("server_port", os.Getenv("SERVER_PORT"))
    os.Setenv("hostname", os.Getenv("DB_CONTAINER_NAME"))
}

When I run docker-compose up --build server everything works despite the error I get as follows:

server_1  | 2022/09/07 11:44:06 failed to load env file: open .env: no such file or directory

However, environments are somehow set.

Here is my docker-compose.yml.

version: '3.8'
services:
  db:
    image: postgres:14.1-alpine
    container_name: ${DB_CONTAINER_NAME}
    restart: always
    environment:
      - POSTGRES_DB=${DB_NAME}
      - POSTGRES_USER=${DB_USERNAME}
      - POSTGRES_PASSWORD=${DB_PASSWORD}
    ports:
      - ${DB_PORT}:${DB_PORT}
    env_file:
     - .env
    volumes:
      - db:/var/lib/postgresql/data
      - ./psql/statements/create-tables.sql:/docker-entrypoint-initdb.d/create_table.sql
  server:
        build:
          context: .
          dockerfile: Dockerfile
        env_file: .env
        depends_on:
         - ${DB_CONTAINER_NAME}
        networks:
           - default
        ports:
         - ${SERVER_PORT}:${SERVER_PORT}
volumes:
  db:
    driver: local

And my Dockerfile for go application.

FROM golang:1.18
WORKDIR /src
COPY go.sum go.mod ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 go build -o /bin/app .

FROM alpine
COPY --from=0 /bin/app /bin/app
ENTRYPOINT ["/bin/app"]

I've altered some of Dockerfile's content I get different errors. What might be the reason for such a problem? Because it fails to load but still works.