Better handling of when the specified port is already in use

helpers/general.go

@@ -15,6 +15,8 @@ package helpers
 
 import (
 	"bytes"
+	"fmt"
+	"net"
 	"strings"
 )
 
@@ -49,3 +51,16 @@ func StripHTML(s string) string {
 	}
 	return output
 }
+
+func FindAvailablePort() (*net.TCPAddr, error) {
+	l, err := net.Listen("tcp", ":0")
+	if err == nil {
+		defer l.Close()
+		addr := l.Addr()
+		if a, ok := addr.(*net.TCPAddr); ok {
+			return a, nil
+		}
+		return nil, fmt.Errorf("Unable to obtain a valid tcp port. %v", addr)
+	}
+	return nil, err
+}