A .env file in the working directory is now optional

internal/config/load.go

@@ -3,6 +3,7 @@ package config
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"log/slog"
 	"os"
 	"strings"
@@ -34,9 +35,13 @@ func isExplicitlySet(key string) bool {
 }
 
 // loadEnv loads environment variables from a .env file in the working
-// directory.
+// directory, if there is one. One that can't be read or parsed is an error.
 func loadEnv() error {
-	if err := godotenv.Load(); err != nil {
+	err := godotenv.Load()
+	if errors.Is(err, fs.ErrNotExist) {
+		return nil
+	}
+	if err != nil {
 		return fmt.Errorf("invalid .env file: %w", err)
 	}
 	return nil