Code cleaning

README.md

@@ -2,3 +2,11 @@
 
 Command to build the executable for manual upload to Lambda:
 GOOS=linux CGO_ENABLED=0 go build -o main .
+
+Required variables:
+
+- FETCH_SIZE: how many news to fetch
+- BATCH_SIZE: batch size for DB write
+- REGION: AWS region
+- SENDER: sender email address
+- RECIPIENT: recipient email address