Allow access and error logging to stdout by configuring a path of "-".

Thanks to @icedquinn@blob.cat for the suggestion.

README.md

@@ -198,10 +198,12 @@ examples of the appropriate syntax.
   `/var/gemini/users/gus/` to `/home/gus/public_gemini/` if you want.
 * `AccessLog`: Path to access log file (default value `access.log`,
   i.e. in the current wrorking directory).  Note that all intermediate
-  directories must exist, Molly Brown won't create them for you.
+  directories must exist, Molly Brown won't create them for you.  Set
+  to `-` for logging to `stdout`.
 * `ErrorLog`: Path to error log file (default value `error.log`, i.e.
   in the current wrorking directory).  Note that all intermediate
-  directories must exist, Molly Brown won't create them for you.
+  directories must exist, Molly Brown won't create them for you.  Set
+  to `-` for logging to `stdout`.
 * `GeminiExt`: Files with this extension will be served with a MIME
   type of `text/gemini` (default value `gmi`).
 * `MimeOverrides`: In this section of the config file, keys are path

main.go

@@ -26,19 +26,29 @@ func main() {
 	}
 
 	// Open log files
-	errorLogFile, err := os.OpenFile(config.ErrorLog, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
-		log.Fatal(err)
+	var errorLogFile *os.File
+	if config.ErrorLog == "-" {
+		errorLogFile = os.Stdout
+	} else {
+		errorLogFile, err = os.OpenFile(config.ErrorLog, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer errorLogFile.Close()
 	}
-	defer errorLogFile.Close()
 	errorLog := log.New(errorLogFile, "", log.Ldate | log.Ltime)
 
-	accessLogFile, err := os.OpenFile(config.AccessLog, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
-		errorLog.Println("Error opening access log file: " + err.Error())
-		log.Fatal(err)
+	var accessLogFile *os.File
+	if config.AccessLog == "-" {
+		accessLogFile = os.Stdout
+	} else {
+		accessLogFile, err = os.OpenFile(config.AccessLog, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+		if err != nil {
+			errorLog.Println("Error opening access log file: " + err.Error())
+			log.Fatal(err)
+		}
+		defer accessLogFile.Close()
 	}
-	defer accessLogFile.Close()
 
 	// Read TLS files, create TLS config
 	cert, err := tls.LoadX509KeyPair(config.CertPath, config.KeyPath)