use go.mod for current sdk rather than file

Author: roothorp

.atlas-sdk-version

@@ -3,7 +3,7 @@
 set -euo pipefail
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-CURRENT_SDK_RELEASE=$(cat "${SCRIPT_DIR}/../.atlas-sdk-version")
+CURRENT_SDK_RELEASE=$(go list -m all | grep go.mongodb.org/atlas-sdk | awk -F '/| ' '{print $3}')
 echo "CURRENT_SDK_RELEASE: $CURRENT_SDK_RELEASE"
 
 LATEST_SDK_TAG=$(curl -sSfL -X GET  https://api.github.com/repos/mongodb/atlas-sdk-go/releases/latest | jq -r '.tag_name')
@@ -16,5 +16,4 @@ echo  "==> Updating SDK to latest major version ${LATEST_SDK_TAG}"
 go tool --modfile tools/toolbox/go.mod gomajor get --rewrite "go.mongodb.org/atlas-sdk/${CURRENT_SDK_RELEASE}" "go.mongodb.org/atlas-sdk/${LATEST_SDK_RELEASE}@${LATEST_SDK_TAG}"
 go mod tidy
 
-echo "$LATEST_SDK_RELEASE" > ".atlas-sdk-version"
 echo "Done"