502 connection refuse while sending requests from docker-compose

I have a golang application that works well locally (I send requests and get the correct responses). But when I try to run this application in containers with nginx proxy server, I get a 502 error for all requests:

[error] 31#31: *1 connect() failed (111: Connection refused) while
connecting to upstream, client: 172.20.0.1, server:
polygon.application.local, request: "GET /v1/credits HTTP/1.1",
upstream: "http://172.20.0.5:8080/v1/credits", host:
"polygon.application.local"

I have tried different solutions from Google to fix this problem, but have not fixed it yet.

There are my configs:

• docker-compose.yaml

version: "3.9"

services:
  nginx:
    image: nginx:alpine
    volumes:
      - ${PROJECT_DIR}/deployments/nginx.conf:/etc/nginx/conf.d/default.conf:delegated
      - ${PROJECT_DIR}/configs/ssl:/etc/nginx/ssl/:delegated
    ports:
      - "80:80"
      - "443:443"

  swagger_ui:
    image: swaggerapi/swagger-ui
    environment:
      SWAGGER_JSON: /spec/api.swagger.yaml
    volumes:
      - ${PROJECT_DIR}/api/openapi-spec/api.swagger.yaml:/spec/api.swagger.yaml

  credit_server:
    build:
      context: ..
      dockerfile: ${PROJECT_DIR}/deployments/Dockerfile
      args:
        BUILD_APP_NAME: credit-server
    depends_on:
      credit_service_db:
        condition: service_healthy

  credit_service_db:
    image: mysql:8.0
    container_name: credit_service_db
    restart: always
    environment:
      MYSQL_DATABASE: credit_service
      MYSQL_USER: credit_service
      MYSQL_PASSWORD: credit_service
      MYSQL_ROOT_PASSWORD: credit_service
    ports:
      - '3306:3306'
    expose:
      - '3306'
    healthcheck:
      test: [ 'CMD-SHELL', 'mysqladmin ping -h localhost' ]
      interval: 5s
      timeout: 20s
      retries: 10

• nginx.conf

map $microservice $upstream {
    credits       credit_server:8080;
    swagger       swagger_ui:8080;
}

server {
    listen 443 http2 ssl;
    server_name polygon.application.local;
    server_tokens   off;
    client_max_body_size 16m;
    root /dev/null;
    resolver 127.0.0.11 valid=30s;

    ssl_certificate     /etc/nginx/ssl/crt.pem;
    ssl_certificate_key /etc/nginx/ssl/private.key.pem;

    location / {
        set $microservice "swagger";
        proxy_pass http://$upstream;
    }

    location ~ ^/v1/(?<microservice>[w-]+) {
        proxy_http_version 1.1;
        proxy_set_header    Host                $http_host;
        proxy_set_header    X-Real-IP           $remote_addr;
        proxy_set_header    X-Forwarded-For     $proxy_add_x_forwarded_for;
        proxy_set_header    X-Forwarded-Proto   http;
        proxy_set_header    X-Frame-Options     SAMEORIGIN;

        if ($request_method = 'OPTIONS') {
            add_header 'Access-Control-Allow-Origin' '*';
            add_header 'Access-Control-Allow-Methods' 'GET,POST,PUT,DELETE,OPTIONS,PATCH';
            add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Access-Control-Allow-Headers,Access-Control-Allow-Origin,Authorization';
            add_header 'Access-Control-Max-Age' 1728000;
            add_header 'Content-Type' 'text/plain; charset=utf-8';
            add_header 'Content-Length' 0;
            return 204;
        }

        add_header 'X-Microservice' '$microservice';
        add_header 'X-Proxy-Pass' '$upstream';
        add_header 'Access-Control-Allow-Origin' '*';
        add_header 'Access-Control-Allow-Methods' 'GET,POST,PUT,DELETE,OPTIONS,PATCH';
        add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range,Access-Control-Allow-Headers,Access-Control-Allow-Origin,Authorization';
        proxy_pass http://$upstream;
    }
}

• Dockerfile for the credit_server

FROM alpine:latest

ARG BUILD_APP_NAME

ENV PROJECT_DIR=/go

RUN apk add tzdata

COPY ./build/${BUILD_APP_NAME} ${PROJECT_DIR}/bin/app
COPY ./configs ${PROJECT_DIR}/configs
COPY ./internal/migrations ${PROJECT_DIR}/migrations

CMD ${PROJECT_DIR}/bin/app -c ${PROJECT_DIR}/configs/config.yml -m container -p ${PROJECT_DIR}/migrations/

All containers start and work without errors.

I also send my requests from swagger and postman