Fix the README sample plugin code and build steps (#3)

Signed-off-by: Martijn Stevenson <[email protected]>

README.md

@@ -1,24 +1,43 @@
 # WebAssembly for Proxies (Go SDK) [![Build](https://github.com/proxy-wasm/proxy-wasm-go-sdk/actions/workflows/workflow.yaml/badge.svg)](https://github.com/proxy-wasm/proxy-wasm-go-sdk/actions) [![License](https://img.shields.io/badge/license-Apache%202.0-blue.svg)](LICENSE)
 
-The Go SDK for
- [Proxy-Wasm](https://github.com/proxy-wasm/spec), enabling developers to write Proxy-Wasm plugins in Go. 
+The Go SDK for [Proxy-Wasm](https://github.com/proxy-wasm/spec), enabling
+developers to write Proxy-Wasm plugins in Go.
 
-Note: This SDK targets the upstream Go compiler, version 1.24 or later. This is different than the forked github.com/tetratelabs/proxy-wasm-go-sdk, which targets the TinyGo compiler.
+Note: This SDK targets the upstream Go compiler, version 1.24 or later. This is
+different than the forked github.com/tetratelabs/proxy-wasm-go-sdk, which
+targets the TinyGo compiler.
 
 ## Project Status
 
-This SDK is based off of github.com/tetratelabs/proxy-wasm-go-sdk; however, it is effectively a new SDK targeting a completely different toolchain. It relies on the not-yet-released Go 1.24 and hasn't seen extensive prod testing by end-users. This SDK is an alpha product.
+This SDK is based off of github.com/tetratelabs/proxy-wasm-go-sdk; however, it
+is effectively a new SDK targeting a completely different toolchain. It relies
+on the not-yet-released Go 1.24 and hasn't seen extensive prod testing by
+end-users. This SDK is an alpha product.
 
 ## Getting Started
 
-- [examples](examples) directory contains the example codes on top of this SDK.
-- [OVERVIEW.md](doc/OVERVIEW.md) the overview of Proxy-Wasm, the API of this SDK, and the things you should know when writing plugins.
+-   [examples](examples) directory contains the example codes on top of this
+    SDK.
+-   [OVERVIEW.md](doc/OVERVIEW.md) the overview of Proxy-Wasm, the API of this
+    SDK, and the things you should know when writing plugins.
 
 ## Requirements
 
-- \[Required] [Go](https://go.dev/): v1.24+ - This SDK leverages Go 1.24's support for [WASI](https://github.com/WebAssembly/WASI) (WebAssembly System Interface) reactors. You can grab a release candidate from the [Go unstable releases page](https://go.dev/dl/#unstable). A stable release of Go 1.24 is [expected in February 2025](https://tip.golang.org/doc/go1.24).
-- \[Required] A host environment supporting this toolchain - This SDK leverages additional host imports added to the proxy-wasm-cpp-host in [PR#427](https://github.com/proxy-wasm/proxy-wasm-cpp-host/pull/427). This has yet to be merged, let alone make its way downstream to Envoy, ATS, nginx, or managed environments.
-- \[Optional] [Envoy](https://www.envoyproxy.io) - To run end-to-end tests, you need to have an Envoy binary. You can use [func-e](https://func-e.io) as an easy way to get started with Envoy or follow [the official instruction](https://www.envoyproxy.io/docs/envoy/latest/start/install).
+-   \[Required] [Go](https://go.dev/): v1.24+ - This SDK leverages Go 1.24's
+    support for [WASI](https://github.com/WebAssembly/WASI) (WebAssembly System
+    Interface) reactors. You can grab a release candidate from the
+    [Go unstable releases page](https://go.dev/dl/#unstable). A stable release
+    of Go 1.24 is
+    [expected in February 2025](https://tip.golang.org/doc/go1.24).
+-   \[Required] A host environment supporting this toolchain - This SDK
+    leverages additional host imports added to the proxy-wasm-cpp-host in
+    [PR#427](https://github.com/proxy-wasm/proxy-wasm-cpp-host/pull/427). This
+    has yet to be merged, let alone make its way downstream to Envoy, ATS,
+    nginx, or managed environments.
+-   \[Optional] [Envoy](https://www.envoyproxy.io) - To run end-to-end tests,
+    you need to have an Envoy binary. You can use [func-e](https://func-e.io) as
+    an easy way to get started with Envoy or follow
+    [the official instruction](https://www.envoyproxy.io/docs/envoy/latest/start/install).
 
 ## Installation
 
@@ -28,7 +47,7 @@ go get github.com/proxy-wasm/proxy-wasm-go-sdk
 
 ## Minimal Example Plugin
 
-A minimal plugin:
+A minimal `main.go` plugin defining VM and Plugin contexts:
 
 ```go
 package main
@@ -38,22 +57,31 @@ import (
     "github.com/proxy-wasm/proxy-wasm-go-sdk/proxywasm/types"
 )
 
+func main() {}
 func init() {
     proxywasm.SetVMContext(&vmContext{})
 }
+
 type vmContext struct {
     types.DefaultVMContext
 }
+func (*vmContext) NewPluginContext(contextID uint32) types.PluginContext {
+    return &pluginContext{}
+}
+
 type pluginContext struct {
     types.DefaultPluginContext
 }
-func (*context) NewPluginContext(contextID uint32) types.PluginContext {
-    return &context{}
-}
-func main() {}
+// pluginContext should implement OnPluginStart, NewHttpContext, NewTcpContext, etc
 ```
 
-It can be compiled with `env GOOS=wasip1 GOARCH=wasm go build -buildmode=c-shared -o my-plugin.wasm main.go`.
+Compile the plugin as follows:
+
+```bash
+$ go mod init main.go
+$ go mod tidy
+$ env GOOS=wasip1 GOARCH=wasm go build -buildmode=c-shared -o my-plugin.wasm main.go
+```
 
 ## Build and run Examples
 
@@ -63,7 +91,7 @@ make build.examples
 
 # Build a specific example using the `go` tool.
 cd examples/helloworld
-env GOOS=wasp1 GOARCH=wasm go build -buildmode=c-shared -o main.wasm main.go
+env GOOS=wasip1 GOARCH=wasm go build -buildmode=c-shared -o main.wasm main.go
 
 # Test the built wasm module using `go test`.
 go test
@@ -75,24 +103,32 @@ make run name=helloworld
 
 ## Compatible Envoy builds
 
-Envoy is the first host side implementation of Proxy-Wasm ABI, 
-and we run end-to-end tests with multiple versions of Envoy and Envoy-based [istio/proxy](https://github.com/istio/proxy) in order to verify Proxy-Wasm Go SDK works as expected.
+Envoy is the first host side implementation of Proxy-Wasm ABI, and we run
+end-to-end tests with multiple versions of Envoy and Envoy-based
+[istio/proxy](https://github.com/istio/proxy) in order to verify Proxy-Wasm Go
+SDK works as expected.
 
-Please refer to [workflow.yaml](.github/workflows/workflow.yaml) for which version is used for End-to-End tests.
+Please refer to [workflow.yaml](.github/workflows/workflow.yaml) for which
+version is used for End-to-End tests.
 
 ## Build tags
 
-The following build tags can be used to customize the behavior of the built plugin. Build tags [can be specified in the `go build` command via the `-tags` flag](https://pkg.go.dev/cmd/go#:~:text=tags):
+The following build tags can be used to customize the behavior of the built
+plugin. Build tags
+[can be specified in the `go build` command via the `-tags` flag](https://pkg.go.dev/cmd/go#:~:text=tags):
 
-- `proxywasm_timing`: Enables logging of time spent in invocation of the plugin's exported functions. This can be useful for debugging performance issues.
+-   `proxywasm_timing`: Enables logging of time spent in invocation of the
+    plugin's exported functions. This can be useful for debugging performance
+    issues.
 
 ## Contributing
 
-We welcome contributions from the community! See [CONTRIBUTING.md](doc/CONTRIBUTING.md) for how to contribute to this repository.
+We welcome contributions from the community! See
+[CONTRIBUTING.md](doc/CONTRIBUTING.md) for how to contribute to this repository.
 
 ## External links
 
-- [WebAssembly for Proxies (ABI specification)](https://github.com/proxy-wasm/spec)
-- [WebAssembly for Proxies (C++ SDK)](https://github.com/proxy-wasm/proxy-wasm-cpp-sdk)
-- [WebAssembly for Proxies (Rust SDK)](https://github.com/proxy-wasm/proxy-wasm-rust-sdk)
-- [WebAssembly for Proxies (AssemblyScript SDK)](https://github.com/solo-io/proxy-runtime)
+-   [WebAssembly for Proxies (ABI specification)](https://github.com/proxy-wasm/spec)
+-   [WebAssembly for Proxies (C++ SDK)](https://github.com/proxy-wasm/proxy-wasm-cpp-sdk)
+-   [WebAssembly for Proxies (Rust SDK)](https://github.com/proxy-wasm/proxy-wasm-rust-sdk)
+-   [WebAssembly for Proxies (AssemblyScript SDK)](https://github.com/solo-io/proxy-runtime)