Environment Variables not loading

Question

Im having a monorepo urn with Turborepo and now want to deploy an express.js service (affects different types of services). Services and its dependecies are building just fine as intended but when running my service, the provided environment-variables (under "Variables" will not come into affect).

I've simply verified it by `console.log(process.env)` which gave me all the default environment variables for NodeJS, Railway and Turbo.  During build variables like `DO_NOT_TRACK=1` will be recognised and take effect.

I've read through the documentation of railpack (and propably missed a very obvious hint)

**railway.json**
```json
{
  "$schema": "https://railway.com/railway.schema.json",
  "build": {
    "builder": "RAILPACK",
    "buildCommand": "npx turbo run build --filter=@budgetbuddyde/backend",
    "watchPatterns": [
      "/services/backend/**",
      "/packages/**"
    ],
    "buildEnvironment": "V3"
  },
  "deploy": {
    "runtime": "V2",
    "numReplicas": 1,
    "startCommand": "echo $AWS_S3_BUCKET_NAME && npx turbo run start --filter=@budgetbuddyde/backend",
    "healthcheckPath": "/api/health",
    "sleepApplication": false,
    "multiRegionConfig": {
      "europe-west4-drams3a": {
        "numReplicas": 1
      }
    },
    "restartPolicyType": "ON_FAILURE"
  }
}
```
**logs**
```txt
@budgetbuddyde/backend:start: /app/services/backend/build/src/lib/s3.js:23
@budgetbuddyde/backend:start:         throw new error_1.EnvironmentVariableNotSetError(missingEnvVars.join(', '));
@budgetbuddyde/backend:start:         ^
@budgetbuddyde/backend:start: 
@budgetbuddyde/backend:start: EnvironmentVariableNotSetError: Environment variable AWS_ENDPOINT_URL, AWS_S3_BUCKET_NAME, AWS_DEFAULT_REGION, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY is not set
@budgetbuddyde/backend:start:     at getS3Client (/app/services/backend/build/src/lib/s3.js:23:15)
@budgetbuddyde/backend:start:     at new AttachmentHandler (/app/services/backend/build/src/lib/attachment/attachment.handler.js:23:46)
@budgetbuddyde/backend:start:     at new TransactionAttachmentHandler (/app/services/backend/build/src/lib/attachment/transaction-attachment.handler.js:10:1)
```