Update Readme with documentation

README.md

@@ -1,10 +1,135 @@
+```markdown
 [![Build Status][gha-workflow-badge]][gha-workflow-url] [![Latest release][gha-latest-release]][gha-releases-url]
 
 # Kong Plugin Development Kit - Go edition
 
-Docs: https://pkg.go.dev/github.com/Kong/go-pdk.
+Docs: https://pkg.go.dev/github.com/Kong/go-pdk
+
+The Kong Plugin Development Kit (PDK) for Go lets you write custom Kong Gateway plugins in Go.
+
+## Getting Started
+
+To write a Kong Gateway plugin in Go:
+
+1. Define a `struct` type to hold configuration.
+2. Write a `New()` function to create instances of your struct.
+3. Add methods to that struct to handle request phases.
+4. Include the `go-pdk/server` sub-library.
+5. Add a `main()` function that calls `server.StartServer(New, Version, Priority)`.
+6. Compile as an executable with `go build`.
+
+## Plugin Structure
+
+### Configuration struct
+
+The plugin uses a Go `struct` to receive configuration from Kong:
+
+```go
+type MyConfig struct {
+    Path   string `json:"my_file_path"`
+    Reopen bool   `json:"reopen"`
+}
+```
+
+### `New()` constructor
+
+Define a function to return a new instance of your config struct:
+
+```go
+func New() interface{} {
+    return &MyConfig{}
+}
+```
+
+### `main()` function
+
+Include `github.com/Kong/go-pdk/server` and start the plugin:
+
+```go
+func main () {
+  server.StartServer(New, Version, Priority)
+}
+```
+
+When run, the plugin creates a socket file within the Kong prefix directory.
+
+### Phase handlers
+
+You can implement logic in the following phases using the same signature:
+
+```go
+func (conf *MyConfig) Access(kong *pdk.PDK) {
+  ...
+}
+```
+
+Supported phases:
+
+- `Certificate`
+- `Rewrite`
+- `Access`
+- `Response` *(enables buffered proxy mode)*
+- `Preread`
+- `Log`
+
+### Version and priority
+
+Set execution order with constants:
+
+```go
+const Version = "1.0.0"
+const Priority = 1
+```
+
+Higher priority runs earlier.
+
+## Configuring with `kong.conf`
+
+To register plugins in Kong, define plugin server settings in `kong.conf`:
+
+```conf
+pluginserver_names = my-plugin
+
+pluginserver_my_plugin_socket = /usr/local/kong/my-plugin.socket
+pluginserver_my_plugin_start_cmd = /usr/local/bin/my-plugin
+pluginserver_my_plugin_query_cmd = /usr/local/bin/my-plugin -dump
+```
+
+The socket and start command lines can be omitted if using defaults.
+
+
+## Using in Containers or Kubernetes
+
+To run Go plugins with Kong Gateway in a container, copy your plugin binary into the Kong image and ensure it is executable by the container.
+
+> **Note:** Kong's official Docker images run as the `nobody` user. Use `USER root` temporarily to install or copy files.
+
+Example `Dockerfile`:
+
+```dockerfile
+FROM kong
+USER root
+
+# Copy your compiled Go plugin into the container
+COPY your-go-plugin /usr/local/bin/your-go-plugin
+RUN chmod +x /usr/local/bin/your-go-plugin
+
+USER kong
+ENTRYPOINT ["/docker-entrypoint.sh"]
+EXPOSE 8000 8443 8001 8444
+STOPSIGNAL SIGQUIT
+HEALTHCHECK --interval=10s --timeout=10s --retries=10 CMD kong health
+CMD ["kong", "docker-start"]
+```
+
+Ensure the plugin path matches the value set in `kong.conf` under `pluginserver_your_plugin_start_cmd`.
+
+## Example Plugins
+
+Explore [example plugins](https://github.com/Kong/go-pdk/tree/master/examples).
 
 [gha-workflow-badge]: https://github.com/Kong/go-pdk/actions/workflows/test.yml/badge.svg
 [gha-workflow-url]: https://github.com/Kong/go-pdk/actions/workflows/test.yml
 [gha-latest-release]: https://img.shields.io/github/v/release/Kong/go-pdk.svg
 [gha-releases-url]: https://github.com/Kong/go-pdk/releases
+```