feat(cache): add Cloudflare SigV4 S3 signature compatibility fix and compile locally

go-cache-plugin-src/README.md

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+# go-cache-plugin
+
+[![GoDoc](https://img.shields.io/static/v1?label=godoc&message=reference&color=lightgrey)](https://pkg.go.dev/github.com/tailscale/go-cache-plugin)
+[![CI](https://github.com/tailscale/go-cache-plugin/actions/workflows/go-presubmit.yml/badge.svg?event=push&branch=main)](https://github.com/tailscale/go-cache-plugin/actions/workflows/go-presubmit.yml)
+
+This repository defines a tool implementing a `GOCACHEPROG` plugin backed by Amazon S3.
+
+## Installation
+
+```shell
+go install github.com/tailscale/go-cache-plugin/cmd/go-cache-plugin@latest
+```
+
+## Usage Outline
+
+```shell
+export GOCACHEPROG="go-cache-plugin --cache-dir=/tmp/gocache --bucket=some-s3-bucket"
+go test ./...
+```
+
+Using the plugin requires a Go toolchain built with `GOEXPERIMENT=cacheprog` enabled.
+However, you do not need the experiment enabled to build the plugin itself.
+
+## Discussion
+
+The `go-cache-plugin` program supports two modes of operation:
+
+1. **Direct mode**: The program is invoked directly by the Go toolchain as a
+   subprocess, and exits when the toolchain execution ends.
+
+   This is the default mode of operation, and requires no additional setup.
+
+2. **Server mode**: The program runs as a separate process and the Go toolchain
+   communicates with it over a local socket.
+
+   This mode requires the server to be started up ahead of time, but makes the
+   configuration for the toolchain simpler. This mode also permits running an
+   in-process module and sum database proxy.
+
+### Server Mode
+
+To run in server mode, use the `serve` subcommand:
+
+```sh
+# N.B.: The --plugin flag is required.
+go-cache-plugin serve \
+   --plugin=5930 \
+   --cache-dir=/tmp/gocache \
+   --bucket=some-s3-bucket
+```
+
+To connect to a server running in this mode, use the `connect` subcommand:
+
+```sh
+# Use the same port given to the server's --plugin flag.
+# Mnemonic: 5930 == (Go) (C)ache (P)lugin
+export GOCACHEPROG="go-cache-plugin connect 5930"
+go build ./...
+```
+
+The `connect` command just bridges the socket to stdin/stdout, which is how the
+Go toolchain expects to talk to the plugin.
+
+### Running a Module Proxy
+
+To enable a caching module proxy, use the `--modproxy` flag to `serve`.  The
+module proxy uses HTTP, not the plugin interface, use `--http` to set the address:
+
+```sh
+go-cache-plugin serve \
+   --plugin=5930 \
+   --http=localhost:5970 --modproxy \
+   --cache-dir=/tmp/gocache \
+   # ... other flags
+```
+
+To tell the Go toolchain about the proxy, set:
+
+```sh
+# Mnemonic: 5970 == (Go) (M)odule (P)roxy
+export GOPROXY=http://localhost:5970/mod   # use the --http address
+```
+
+If you want to also proxy queries to `sum.golang.org`, also add:
+
+```sh
+export GOSUMDB='sum.golang.org http://locahost:5970/mod/sumdb/sum.golang.org'
+```
+
+## References
+
+- [Cache plugin protocol (proposal)](https://github.com/golang/go/issues/59719)
+- [Cache plugin library](https://github.com/creachadair/gocache)
+- [Go module proxy documentation](https://proxy.golang.org)