Allow to override instance type (closes #39)

prepare-vms/docker-compose.yml

@@ -15,5 +15,6 @@ services:
             AWS_ACCESS_KEY_ID: ${AWS_ACCESS_KEY_ID}
             AWS_SECRET_ACCESS_KEY: ${AWS_SECRET_ACCESS_KEY}
             AWS_DEFAULT_REGION: ${AWS_DEFAULT_REGION}
+            AWS_INSTANCE_TYPE: ${AWS_INSTANCE_TYPE}
             USER: ${USER}
         entrypoint: /root/prepare-vms/workshopctl

prepare-vms/lib/commands.sh

@@ -280,7 +280,7 @@ _cmd_start() {
     result=$(aws ec2 run-instances \
         --key-name $AWS_KEY_NAME \
         --count $COUNT \
-        --instance-type t2.medium \
+        --instance-type ${AWS_INSTANCE_TYPE-t2.medium} \
         --client-token $TOKEN \
         --image-id $AMI)
     reservation_id=$(echo "$result" | head -1 | awk '{print $2}')