📝 Add README.md

README.md

@@ -1,5 +1,50 @@
 # gcf-fetch
 
-See:
+Cloud Functions that retrieve data from public APIs and store it in Google Cloud Storage.<br>
+Google Cloud Functions Gen2 Golang environment is supported.
+
+# Features
+
+- Fetch data is stored in a path based on the API's URL, like [ghq](https://github.com/x-motemen/ghq).
+  - Therefore, even if you get various API data, you do not need to manage the bucket's path.
+- Execute Cloud Pub/Sub as a trigger.
+  - Therefore, periodic execution is also possible with [Cloud Scheduler](https://cloud.google.com/scheduler).
+- Fetch data is managed by [Object Versioning](https://cloud.google.com/storage/docs/object-versioning).
+- GCS [price](https://cloud.google.com/storage/pricing) are optimized by [Object Lifecycle Management](https://cloud.google.com/storage/docs/lifecycle).
+  - The storage class is set to change from Standard to Coldline after 7 days from object creation and from Coldline to Archive after 30 days (easy to change).
+- [zl](https://github.com/nkmr-jp/zl) (zap based logger) for logging by level.
+  - Log in JSON format so it can check the element contents in detail with [Cloud Logging](https://cloud.google.com/logging).
+  - You can also check the contents of CloudEvents triggered by Functions in the log.
+
+
+# Prepare
+
+If you haven't already, install and set up the [Cloud SDK](https://cloud.google.com/sdk/docs/install-sdk).
+
+# Usage
+
+Create various GCP resources
+```sh
+make init
+```
+
+Run test
+```sh
+make test
+```
+
+Deploy to google cloud functions
+```sh
+make deploy
+```
+
+Send pub/sub event
+```sh
+make send URL="https://api.github.com/users/github"
+```
+
+
+
+# See
 - https://github.com/GoogleCloudPlatform/golang-samples/tree/main/functions/functionsv2
 - https://cloud.google.com/functions/docs/2nd-gen/getting-started#pubsub