Configure Nginx to serve Static files of Angular and also reverse proxy for express

Question

i'm very new to Nginx and want to use it for serving static angular files and also proxy to a backend express server. I'm also dockerizing the frontend (with nginx) and the backend.

In the frontend i only have a button thats making a request and getting some data from express. Everytime i try this, im getting a bad gateway error.

Something is wrong but i dont have the experience to firure it out, please help.

here is a link to the Simple Projekt setup: https://github.com/stabkara/nginx-app

Front End

dockerfile

# Stage 1: Compile and Build angular codebase

# Use official node image as the base image
FROM node:latest as build

# Set the working directory
WORKDIR /usr/src/app

# Add the source code to app
COPY ./ /usr/src/app/

# Install all the dependencies
RUN npm install

# Generate the build of the application
RUN npm run build


# Stage 2: Serve app with nginx server

# Use official nginx image as the base image
FROM nginx:latest

# Copy the build output to replace the default nginx contents.
COPY --from=build /usr/src/app/dist/nginx-app /usr/share/nginx/html
COPY /nginx.conf  /etc/nginx/conf.d/default.conf

# Expose port 80
EXPOSE 80

nginx.conf

server {
  listen 80;
  sendfile on;
  default_type application/octet-stream;

  gzip on;
  gzip_http_version 1.1;
  gzip_disable      "MSIE [1-6]\.";
  gzip_min_length   256;
  gzip_vary         on;
  gzip_proxied      expired no-cache no-store private auth;
  gzip_types        text/plain text/css application/json application/javascript application/x-javascript text/xml application/xml application/xml+rss text/javascript;
  gzip_comp_level   9;

  location / {
    root /usr/share/nginx/html;
    try_files $uri $uri/ /index.html =404;
  }

  location /api {
    
    proxy_http_version 1.1;
    proxy_cache_bypass $http_upgrade;

    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection 'upgrade';
    proxy_set_header Host $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 $scheme;

    
    proxy_pass http://localhost:3000/api;
  }

}

request executed after clicking the button

test() {
    this.http.get(environment.apiUrl + '/array').subscribe((data) => console.log(data))
  }

environment.prod.ts (guess here is the mistake maybe)

export const environment = {
  production: true,
  apiUrl: '/api'
};

Backend

dockerfile

FROM node:16

# Create app directory
WORKDIR /usr/src/app

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ./

RUN npm install
# If you are building your code for production
# RUN npm ci --only=production

# Bundle app source
COPY . .

EXPOSE 3000
CMD [ "node", "index.js" ]

index.js

const express = require("express");
const app = express();
var cors = require("cors");
const router = express.Router();
const routes = require("./routes")(router, {});
app.use("/api", routes);

app.use(cors());

// Setting the server to listen at port 3000
app.listen(3000, function (req, res) {
  console.log("Server is running at port 3000");
});

routes

module.exports = (app) => {
  app.get("/", function (req, res) {
    res.json({
      number: 1,
    });
  });

  // Defining get request at '/multiple' route
  app.get("/multiple", function (req, res) {
    res.json({
      number: 1,
      name: "John",
      gender: "male",
    });
  });

  // Defining get request at '/array' route
  app.get("/array", function (req, res) {
    res.json([
      {
        number: 1,
        name: "John",
        gender: "male",
      },
      {
        number: 2,
        name: "Ashley",
        gender: "female",
      },
    ]);
  });

  return app;
};

I hope you can help me. It would be awesome! Thanks in advance! (Serving static files is working, but the proxy not)