Angular and Asp dot net core Web API connection issue

HI All,

I am a very basic learner of Docker.
I have a Asp.net core Web Service, and an Angular app running:

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
ea6a1550d89a minirws:v12 “nginx -g 'daemon of…” 11 hours ago Up 8 seconds 0.0.0.0:4000->80/tcp minirwscontainer
cf405ad4d563 examservice:v9 “dotnet ExamService.…” 15 hours ago Up 4 hours 0.0.0.0:8080->80/tcp examservicecontainer

Both running in a isolated network.
the proxy.config.json file of the angular app is.
{

“/api”: {

"target": "http://examservicecontainer",

"secure": false,

"logLevel": "debug",

"changeOrigin": false

}

}

The Angular App is not able to connect to the Web API , getting a 404 error.
Can anyone help me with what the issue is?

Docker File of the Angular Application:
FROM node:latest as node

WORKDIR /app

COPY package.json package.json

COPY proxy.conf.json proxy.conf.json

RUN npm install

COPY . .

RUN npm run build --prod

stage 2

FROM nginx:alpine

COPY --from=node /app/dist/miniRws /usr/share/nginx/html

EXPOSE 4000:80