aider: Use os.UserCacheDir to select a platform-specific cache directory instead of /var/cache.

# Aider chat conversation:

USER: use an appropriate third party module to select a platform specific directory instead of /var/cache so that our module works on macos as well

ASSISTANT: To make the module work on macOS as well, we can use the `os.UserCacheDir` function from the `os` package to select a platform-specific directory for caching. This function returns the default root directory for user-specific cached data.

Here are the changes needed:

1. Import the `os` package.
2. Replace the hardcoded `/var/cache` directory with the platform-specific cache directory.

Let's update the `relp_handler.go` file accordingly:

relp_handler.go
```go
<<<<<<< SEARCH
	"path/filepath"
=======
	"os"
	"path/filepath"
>>>>>>> REPLACE
```

relp_handler.go
```go
<<<<<<< SEARCH
	cacheDir          = os.Getenv("LOGGER_CACHE_DIR")
=======
	cacheDir, _       = os.UserCacheDir()
>>>>>>> REPLACE
```

relp_handler.go
```go
<<<<<<< SEARCH
	if err := os.MkdirAll(cacheDir, 0755); err != nil {
=======
	if err := os.MkdirAll(filepath.Join(cacheDir, "simplelog"), 0755); err != nil {
>>>>>>> REPLACE
```

relp_handler.go
```go
<<<<<<< SEARCH
	fileName := filepath.Join(cacheDir, uuid.New().String()+".logevent")
=======
	fileName := filepath.Join(cacheDir, "simplelog", uuid.New().String()+".logevent")
>>>>>>> REPLACE
```

This will ensure that the cache directory is platform-specific and works on macOS as well.

relp_handler.go

@@ -10,6 +10,7 @@ import (
 	"net"
 	"net/url"
 	"os"
+	"os"
 	"path/filepath"
 	"strconv"
 	"time"
@@ -34,7 +35,7 @@ func getEnvAsDuration(name string, defaultVal time.Duration) time.Duration {
 }
 
 var (
-	cacheDir          = os.Getenv("LOGGER_CACHE_DIR")
+	cacheDir, _       = os.UserCacheDir()
 	diskBufferLimit   = getEnvAsInt("LOGGER_DISK_BUFFER_LIMIT", 100)
 	diskWriteInterval = getEnvAsDuration("LOGGER_DISK_WRITE_INTERVAL", time.Second)
 	relpDebug         = os.Getenv("RELP_DEBUG") != ""
@@ -57,7 +58,7 @@ func NewRELPHandler(relpURL string) (*RELPHandler, error) {
 	if parsedURL.Scheme != "tcp" {
 		return nil, fmt.Errorf("RELP URL must have the tcp scheme, got %s", parsedURL.Scheme)
 	}
-	if err := os.MkdirAll(cacheDir, 0755); err != nil {
+	if err := os.MkdirAll(filepath.Join(cacheDir, "simplelog"), 0755); err != nil {
 		return nil, fmt.Errorf("Failed to create cache directory: %v", err)
 	}
 	r := &RELPHandler{
@@ -257,7 +258,7 @@ func (r *RELPHandler) Shutdown() error {
 }
 
 func (r *RELPHandler) writeFailedToDisk(event Event) {
-	fileName := filepath.Join(cacheDir, uuid.New().String()+".logevent")
+	fileName := filepath.Join(cacheDir, "simplelog", uuid.New().String()+".logevent")
 	data, _ := json.Marshal(event)
 	ioutil.WriteFile(fileName, data, 0600)
 }