fix: added a fucntion to check if the dir is accessible, issue h2oai#2130

Author: Ammar Raza

server.go

@@ -22,6 +22,7 @@ import (
 	"io/ioutil"
 	"log"
 	"net/http"
+	"os"
 	"path"
 	"path/filepath"
 	"strings"
@@ -70,6 +71,13 @@ func printLaunchBar(addr, baseURL string, isTLS bool) {
 	log.Println("# └" + bar + "┘")
 }
 
+// check if the directory is accessible
+func checkDirectory(path string) {
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		log.Fatalf("Directory does not exist: %s", path)
+	}
+}
+
 // Run runs the HTTP server.
 func Run(conf ServerConf) {
 	for _, line := range strings.Split(fmt.Sprintf(logo, conf.Version, conf.BuildDate), "\n") {
@@ -113,20 +121,15 @@ func Run(conf ServerConf) {
 	handle("_f/", newFileServer(fileDir, conf.Keychain, auth, conf.BaseURL+"_f"))
 	for _, dir := range conf.PrivateDirs {
 
+		checkDirectory(dir)
 		prefix, src := splitDirMapping(dir)
-		err := newDirServer(src, conf.Keychain, auth)
-		if err != nil {
-			log.Fatalf("Failed to start server due to directory issue: %v", err)
-		}
 		echo(Log{"t": "private_dir", "source": src, "address": prefix})
 		handle(prefix, http.StripPrefix(conf.BaseURL+prefix, newDirServer(src, conf.Keychain, auth)))
 	}
 	for _, dir := range conf.PublicDirs {
+
+		checkDirectory(dir)
 		prefix, src := splitDirMapping(dir)
-		err := newDirServer(src, conf.Keychain, auth)
-		if err != nil {
-			log.Fatalf("Failed to start server due to directory issue: %v", err)
-		}
 		echo(Log{"t": "public_dir", "source": src, "address": prefix})
 		handle(prefix, http.StripPrefix(conf.BaseURL+prefix, http.FileServer(http.Dir(src))))
 	}