Error connecting Mysql from Go REST API with Docker Compose

I'm very new to Docker, and I'm trying to dockerize a Go REST API and MySQL database to communicate with each other using Docker Compose. I am getting the error [main] Error 1049: Unknown database 'puapp'

Docker compose:

version: '3'
services:
  db:
    build: ./mysql/ 
    restart: always
    environment:
      - MYSQL_ROOT_PASSWORD=root
    volumes:
      - db_volume:/var/lib/mysql

  api-service:
    restart: always
    build: ./
    ports:
      - "8080:80"
    environment:
      - DB_USER=root
      - DB_PASS=root
      - DB_ADDRESS=db:3306
      - DB_PROTOCOL=tcp
      - DB_NAME=puapp
    depends_on:
      - db
    links:
      - db

volumes:
  db_volume:

Dockerfile for go service:

# syntax=docker/dockerfile:1

# Build stage
FROM golang:1.16-alpine AS builder
WORKDIR /app
COPY . .
RUN go mod download
WORKDIR /app/src/main
RUN go build -o restserv


# Run stage
FROM alpine:3.13
WORKDIR /app
COPY --from=builder /app/src/main/restserv .
EXPOSE 8080

CMD "./restserv"

Dockerfile for MySQL:

FROM mysql:latest
ADD dump.sql /docker-entrypoint-initdb.d

Full code - https://github.com/bens-schreiber/restservproj Let me know if I need to add anything